Method for fabricating an amplification gap of an avalanche particle detector

A method for fabricating an amplification gap of an avalanche particle detector in which two parallel electrodes (6, 8) are spaced apart by dielectric spacer elements, comprising the steps of:

• forming a foil including a first electrode layer (30), a bulk layer (32) comprising a dielectric material on said first electrode layer (30), and a second electrode layer (34) parallel to said first electrode layer (30) on said bulk layer (32), wherein said second electrode layer (34) comprises a plurality of holes (18) extending through said second electrode layer (34);
• forming a plurality of gaps (36) in said bulk layer (32) in correspondence to said plurality of holes (18) in said second electrode layer (34) by means of etching, wherein said gaps (36) extend through said bulk layer (32) in a vertical direction thereof to said first electrode layer (30) and in a horizontal direction thereof parallel to said second electrode layer (34) so that said second electrode layer (34) is at least partially undercut by said gaps (36),
• wherein said gaps (36) are etched using an aqueous solution comprising ethylenediamine and potassium hydroxide;
• and
• wherein neighbouring holes (18) in said second electrode layer (34) are formed at varying mutual distances, said varying mutual distances comprising a first distance (d1) and a second distance (d2) greater than said first distance (d1), and wherein the bulk layer between neighbouring gaps (36) is entirely removed by means of the etching between gaps (36) that are formed from neighbouring holes (18) at said first distance (d1), and wherein spacer elements (38) of bulk material are left by the etching between those gaps (36) that are formed from neighbouring holes (18) at said second distance (d2).