Ultra uniform arrays of micro patterns on large area substrate by employing wet chemical etching

Abstract

A wet chemical selective etching process is presented to delineate ultra-uniform micro patterns in the form of arrays of sensor chips of 4mm×4mm size in the matrix of 9×9 on a 3″ diameter silicon substrate with uniform physical and electrical characteristics. The selective etching of thin film is confined to the top area by masking its outer edges. This leads to uniform etching of the entire film leading to ultra-uniform delineation of arrays of micro patterns. The process has been verified over the selective etching of doped polysilicon in defining the polysilicon resistors and subsequently has been applied on realizing Ti/Au interconnecting lines using wet chemical etchant. Experimental results are presented with physical and electrical characteristics of the patterned structures in the statistical form over the substrate surface. SEM analysis is carried out for physical dimension measurement and standard deviation of 0.0040 is observed in polysilicon micro patterning. The process is competitive with reactive ion etching (RIE) in terms of yield, reliability and repeatability with cost effectiveness in a production environment. Methodology of ultra-uniform etching on entire substrate area is developed in support of the experimental results. The ratio of Top Surface Area (TSA) and Total Exposed Surface Area (TESA) is shown as crucial parameter for the uniform etching of thin films.