Electrolyte-Insulator-Semiconductor pH Sensors with Arrayed Patterns Manufactured by Nano Imprint Technology

Abstract

This work focuses on the sensing properties of electrolyte-insulator-semiconductor (EIS) pH sensors with arrayed patterns manufactured by integrating nano imprint technology (NIL) and CMOS process. The arrayed patterns, made of line and square at about ∼200-400nm with a width/space ratio of about ∼1/1-1/2, were fabricated by NIL; followed by the manufacturing of the EIS sensors. The patterns were studied by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The sensors, with arrayed patterns, all exhibited higher sensitivity, lower hysteresis, and lower drift properties than the single one did. The effects of arrayed patterns (square or line) and pattern density on the sensing area were also investigated. With this approach, the sensors can be fabricated for future high performance biochemical sensing applications.

Capacitive Field-Effect EIS Chemical Sensors and Biosensors: A Status Report

“…Field-effect pH sensors based on an EIS system detect potential (charge) changes at the electrolyte/gate-insulator interface, resulting from the changes in the local or bulk pH. It is known that the gate-insulator material in the first ISFET was SiO 2 , which is not the best pH-sensitive material, having a low sensitivity, a narrow linear pH range, a relatively high drift, and a large hysteresis (see, e.g., [9,30,31]). Therefore, other oxides, like Al 2 O 3 [32][33][34], Ta 2 O 5 [29,35,36], ZrO 2 [37], HfO 2 [38][39][40][41], CeO 2 [42], Gd 2 O 3 [43,44], Ti-doped Gd 2 O 3 [45], Lu 2 O 3 [46], Nd 2 O 3 [47], Yb 2 O 3 [48], Dy 2 TiO 5 [49], Er 2 TiO 5 [50], PbTiO 3 [51], YTi x O y [52], Tm 2 Ti 2 O 7 [53], and barium strontium titanate (BST) [54][55][56], as well as Si 3 N 4 [32,57] and nanocrystalline diamond (NCD) [58], have been proven as pH-sensitive gate insulators for EIS sensors.…”

Miniaturized pH‐Sensitive Field‐Effect Capacitors with Ultrathin Ta2O5Films Prepared by Atomic Layer Deposition

“…However, while providing a stable Si-SiO 2 interface with a low density of states, it suffers from a low pH sensitivity, a restricted linear pH range as well as a relatively large drift and hysteresis. [9,26,27] Therefore, plenty of thin-film high-κ materials (e.g., Si 3 N 4 , [28][29][30] Al 2 O 3 , [30][31][32] Ta 2 O 5 , [1,[33][34][35] ZrO 2 , [36,37] HfO 2 , [38][39][40] CeO 2 , [41] TiO 2 , [42] SnO 2 , [43] Gd 2 O 3 , [44] and barium strontium titanate, [45,46] just to name a few) have been studied as pH-sensitive gate insulators in electrolyte-gated field-effect devices, in particular, in EISCAPs. These films were deposited either directly on the Si substrate to replace the SiO 2 or on a SiO 2 layer as stacked gate insulators.…”

“…Among different high-κ dielectrics utilized in pH-sensitive field-effect devices, amorphous Ta 2 O 5 films have been recognized as one of the best pH-sensitive materials, [19] having a large surface buffer capacity, high refractive index (%2.2), relatively wide bandgap (%4.3 eV), high dielectric constant (22)(23)(24)(25)(26)(27)(28), low leakage current, and good dielectric breakdown strength. [50] Moreover, in addition to the high pH-sensitive behavior, Ta 2 O 5 films possess corrosion-resistant properties, making them very attractive for the application in cleaning-in-place or sterilize-in-place, suitable "nonglass" pH sensors for in-line process monitoring (e.g., in biotechnology, food, and pharmaceutical industry).…”

Field‐Effect Transistor‐Based Biosensor for pH Sensing and Mapping

“…There are abundant corners and sidewalls in the channel layer, where ions diffusing to the sensing film constitute a high local electric field and forbid the ions to close the surface. [94][95][96] In this case, the extraneous ions of the sensing film are dropping, resulting in improved hysteresis. Another is the "passivation" parameter, in which the passivation layer could safeguard the semiconductor channel from extrinsic ions to build up religious hysteresis.…”