Effects of various ion-typed surfactants on silicon anisotropic etching properties in KOH and TMAH solutions

Chii-Rong Yang, Po Ying Chen, Cheng Hao Yang, Yuang Cherng Chiou, Rong Tsong Lee

Research output: Contribution to journalArticle

62 Citations (Scopus)

Abstract

Three ion-typed surfactants, including anionic SDSS, cationic ASPEG and non-ionic PEG, which are powerful wetting agents in electroforming, were added to 30 wt.% KOH and 10 wt.% TMAH solutions to evaluate the silicon anisotropic etching properties of the (1 0 0) silicon plane without agitation and no IPA additive. The results indicate that the surfactant ion-types are not the main determinants of the silicon anisotropic etching properties in KOH and TMAH solutions. The wetting capacity of the etchants causes the efficacies of the etchants on the roughness to follow the order anionic SDSS, cationic ASPEG, non-ionic PEG and pure solution in KOH solutions, and the order cationic ASPEG, non-ionic PEG, pure solution and anionic SDSS in TMAH solutions, especially at higher etching temperatures. Moreover, the chemical activities of etchants differ so that the etching rates follow the order anionic SDSS, pure solution, non-ionic PEG and cationic ASPEG in KOH solutions, and the order anionic SDSS, pure solution, cationic ASPEG and non-ionic PEG in TMAH solutions at a given etching temperature. Anionic SDSS has the highest etching rate of 5.4 μm/min and the lowest surface roughness of 7.5 nm, which are about 1.69 times higher and 7.87 times lower, respectively, than those obtained in pure KOH solution. The cationic ASPEG has a reasonable etching rate of 0.7 μm/min and the lowest surface roughness of 4 nm in TMAH solutions for etching temperature of 100 °C. Furthermore, the surfactants used here were demonstrated to allow the utilization of usual mask materials and anionic SDSS can even increase the selectivity of silicon dissolution toward silicon dioxide in KOH solutions. A drastic reduction of the undercutting of the convex corners is obtained in TMAH solutions with non-ionic PEG surfactant. This finding reveals that the addition of non-ionic PEG to TMAH solutions is ideal when accurate profiles are required without extremely deep etching.

Original languageEnglish
Pages (from-to)271-281
Number of pages11
JournalSensors and Actuators, A: Physical
Volume119
Issue number1
DOIs
Publication statusPublished - 2005 Mar 28

Fingerprint

Anisotropic etching
Silicon
Surface-Active Agents
Surface active agents
surfactants
etching
Ions
silicon
Polyethylene glycols
ions
Etching
etchants
Surface roughness
wetting
surface roughness
Wetting Agents
Wetting agents
Electroforming
electroforming
agitation

Keywords

  • Anisotropic etching
  • Chemical activity
  • Surfactant
  • Undercut
  • Wetting capacity

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Instrumentation
  • Condensed Matter Physics
  • Surfaces, Coatings and Films
  • Metals and Alloys
  • Electrical and Electronic Engineering

Cite this

Effects of various ion-typed surfactants on silicon anisotropic etching properties in KOH and TMAH solutions. / Yang, Chii-Rong; Chen, Po Ying; Yang, Cheng Hao; Chiou, Yuang Cherng; Lee, Rong Tsong.

In: Sensors and Actuators, A: Physical, Vol. 119, No. 1, 28.03.2005, p. 271-281.

Research output: Contribution to journalArticle

Yang, Chii-Rong ; Chen, Po Ying ; Yang, Cheng Hao ; Chiou, Yuang Cherng ; Lee, Rong Tsong. / Effects of various ion-typed surfactants on silicon anisotropic etching properties in KOH and TMAH solutions. In: Sensors and Actuators, A: Physical. 2005 ; Vol. 119, No. 1. pp. 271-281.
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AB - Three ion-typed surfactants, including anionic SDSS, cationic ASPEG and non-ionic PEG, which are powerful wetting agents in electroforming, were added to 30 wt.% KOH and 10 wt.% TMAH solutions to evaluate the silicon anisotropic etching properties of the (1 0 0) silicon plane without agitation and no IPA additive. The results indicate that the surfactant ion-types are not the main determinants of the silicon anisotropic etching properties in KOH and TMAH solutions. The wetting capacity of the etchants causes the efficacies of the etchants on the roughness to follow the order anionic SDSS, cationic ASPEG, non-ionic PEG and pure solution in KOH solutions, and the order cationic ASPEG, non-ionic PEG, pure solution and anionic SDSS in TMAH solutions, especially at higher etching temperatures. Moreover, the chemical activities of etchants differ so that the etching rates follow the order anionic SDSS, pure solution, non-ionic PEG and cationic ASPEG in KOH solutions, and the order anionic SDSS, pure solution, cationic ASPEG and non-ionic PEG in TMAH solutions at a given etching temperature. Anionic SDSS has the highest etching rate of 5.4 μm/min and the lowest surface roughness of 7.5 nm, which are about 1.69 times higher and 7.87 times lower, respectively, than those obtained in pure KOH solution. The cationic ASPEG has a reasonable etching rate of 0.7 μm/min and the lowest surface roughness of 4 nm in TMAH solutions for etching temperature of 100 °C. Furthermore, the surfactants used here were demonstrated to allow the utilization of usual mask materials and anionic SDSS can even increase the selectivity of silicon dissolution toward silicon dioxide in KOH solutions. A drastic reduction of the undercutting of the convex corners is obtained in TMAH solutions with non-ionic PEG surfactant. This finding reveals that the addition of non-ionic PEG to TMAH solutions is ideal when accurate profiles are required without extremely deep etching.

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