Effects of thickness effect and rapid thermal annealing on pH sensing characteristics of thin HfO2 films formed by atomic layer deposition

Tseng Fu Lu*, Hao Chun Chuang, Jer Chyi Wang, Chia Ming Yang, Pei Chun Kuo, Chao Sung Lai

*Corresponding author for this work

Research output: Contribution to journalJournal Article peer-review

9 Scopus citations

Abstract

In this article, thin hafnium oxide (HfO2) films deposited by atomic layer deposition (ALD) were investigated as a sensing layer on an electrolyteinsulator-semiconductor (EIS) structure for pH sensor applications. Compared with sputtering, ALD provides the possibility of shrinking the thickness of the HfO2 sensing layer down to 3.5 nm with a low drift coefficient (<0.2mV/h). To increase the pH response, an additional rapid thermal annealing was performed on a 3.5-nm-thick ALD-HfO2 film. After annealing at 900 °C, the pH sensitivity could be effectively increased to that near the Nernstian response (59.6 mV/pH), and the drift coefficient (<1 mV/h) and hysteresis width (4.26 mV) are still sufficient. On the basis of the results of atomic force microscopy (AFM) analysis, the increase in surface roughness is possibly the reason for the increase in pH response after annealing. For compatibility with advanced complementary metal-oxide- semiconductor (CMOS) technology, the thin ALD-HfO2 film is a promising candidate for pH sensor fabrications.

Original languageEnglish
JournalJapanese Journal of Applied Physics
Volume50
Issue number10 PART 2
DOIs
StatePublished - 10 2011

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