Confined etchant layer technique for two-dimensional lithography at high resolution using electrochemical scanning tunnelling microscopy

Abstract

In order to realize two-dimensional lithography at high resolution (several tens of nanometres), a new approach to the lithography of a fine pattern using a confined etchant layer technique (CELT) in an electrochemical system is presented. A mould plate of conductive material with a highresolution line pattern (which can be prepared with the aid of e.g. electron beams) is used instead of the tip in scanning tunnelling microscopy (STM). The etchant species is generated at the surface of the mould plate by electrochemical photochemical or photoelectrochemical methods, then diffuses away from the surface of the mould plate. The key feature of CELT is the design of a chemical reaction which rapidly destroys the etchant (e.g. within microseconds on average) following its generation. Therefore, the gradient of the concentration of etchant can be greatly enhanced and the thickness of the diffusion layer can be greatly decreased to several tens of nanometres. Thus, the etchant layer is confined and its outer boundary can essentially retain the fine structure of the pattern of the mould plate. Then the substrate to be corroded is adjusted by ECSTM to approach the mould plate within several tens of nanometres and the corroded pattern can retain the fine structure giving a resolution of several tens of nanometres.

Microfabrication of a Diffractive Microlens Array on n‐GaAs by an Efficient Electrochemical Method

“…The etching resolution is determined by the thickness of the CEL (l) and it can be estimated from the value of the step height or the diameter of the concentric rings. We have deduced theoretically that it depends on the diffusion coefficient of the etchant (D) and on the pseudo-first-order reaction rate of the scavenger with Br 2 (Ks): [29] l D=Ks…”

“…All these techniques are relatively expensive and inconvenient when applied to the fabrication of 8-level diffractive microlens arrays. An electrochemical micromachining technique, named the confined etchant layer technique (CELT), was developed by Tian et al [29] Although it has been applied to fabricate microstructures on GaAs and Si, [30,31] the best resolution for this technique is still hundreds of nanometers and it is very difficult to realize large-scale microfabrication. Here, a new process for CELT combined with a hot embossing technique (HET) is proposed for the fabrication of diffractive microlens arrays and the procedure is shown as follows (Scheme 1).…”

A potential method for electrochemical micromachining of titanium alloy Ti6Al4V

“…In this paper we present an electrochemical bulk micromachining method named the confined etchant layer technique (CELT) [28][29][30][31][32] for micromachining titanium and its alloys. The fundamentals of CELT can be described as follows: The etchant is generated electrochemically on the surface of a machining tool or a mold with desired 3D microstructures.…”

“…The thickness of the confined etchant layer (l) can be estimated as: l = (D/ks) 1/2 [32], where D is the diffusion coefficient of the etchant in the solution.…”

Etching and smooth processing of GaAs surface based on the confined etchant layer technique

“…Therefore, a new micro-nano manufacturing method that can meet these requirements simultaneously is strongly required. Recently, the confined etchant layer technique (CELT) proposed by Tian et al (1992) can meet all three requirements mentioned above at the same time. For example, Sun et al (2001) chose the electro-generated bromide as the etching agent and chose H 3 AsO 3 as the scavengers.…”