Experimental investigation of high Si/Al selectivity during anisotropic etching in tetra-methyl ammonium hydroxide

Abstract

This work contributes to the understanding of anisotropic etching of silicon, for microsystems technology, by studying Si/Al selectivity during anisotropic etching of silicon in tetra-methyl ammonium hydroxide (TMAH). By under-etch experiments using a wagon-wheel mask pattern, Si/Al selectivity is studied in relation to trends in etch anisotropy, etched surface morphology, and variations of under-etch behavior with mask-edge angle. TMAH at 5 wt % is used, with or without the additives: dissolved silicon and ammonium persulfate. High Si/Al selectivity is accompanied by obvious changes in the roughness, flatness, and etch rate of the {100} cavity bottoms, by large changes in anisotropy as seen in under-etch rate curves, by lower ratio of {101} to {100} etch rates, and by more regular 〈101〉-oriented steps on non-{111} cavity sidewalls. The conditions are consistent with a low rate of attack of 〈101〉-directed periodic bond chains in the Si lattice.

Preparation and use of a mesoporous silicate material for the removal of tetramethyl ammonium hydroxide (TMAH) from aqueous solution

“…Tetramethyl ammonium hydroxide (TMAH) is a corrosive compound used as a developer in industrial printing, as an organic aqueous alkaline etchant in the electronics sector,1, 2 and as a cleaning solution in semiconductor processing. It is also used in large scale integration processing as a positive photoresist developer 3–5.…”

An Investigation into the Adsorption Characteristics of Grafted Mesoporous Silicates for the Removal of Tetramethyl Ammonium Hydroxide from Aqueous Solution

“…TMAH is used as a developer in industrial printing and as an organic aqueous alkaline etchant in the electronics sector (Pandy et al 1998;Tabata et al 1992). Typically, low concentrations of TMAH are present in the process wastewaters from these sources and there is a need to remove, recover and recycle the TMAH from an economic and environmental perspective.…”

Micro and nanofabrication of SiGe/Ge bridges and membranes by wet-anisotropic etching

“…TMAH and KOH allow a high selectivity between etching rates in h0 0 1i and h1 1 1i directions in the silicon bulk [12]. For this reason they have been widely used in order to create suspended structures, for example by an etch against the etch-resistive {1 1 1} planes in Si(0 0 1) substrates [16,17] or by exploiting the underetching rates of a Si(0 0 1) substrate [18,19]. Germanium is extremely chemically resistive against KOH or TMAH [20,21], so it is potentially an excellent material for this kind of micromachining.…”