Passive Wireless Monitoring of Wafer Cleanliness during Rinsing of Semiconductor Wafers

Xu Zhang, Jun Yan, Bert Vermeire, Farhang Shadman, Junseok Chae

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


Semiconductor facilities consume large amounts of water, most of which is used for rinsing of wafers during cleaning steps. To optimize water use, real-time and in situ monitoring of wafer cleanliness during rinsing is necessary. Yet no prior art is real-time and in situ. In this paper, we present a passive wireless sensing system capable of measuring the residual contamination on the wafers in real-time and in situ. The wireless system consists of a micromachined Electro-Chemical Residue Sensor (ECRS) and wireless transponder circuitry based on RFID technology. The ECRS measures the impurities concentration of the water inside micro-features during the rinsing processes. The sensor reading is converted to a frequency by the on-wafer transponder and remotely logged through a wireless link between two coupled inductors, while the transponder captures power from the remote RF signal: a battery-free system. A prototype system was fabricated and its frequency output was characterized by using sodium chloride solution ranging from 190 ppb to 6 ppm. The measured wireless chemical sensor system has a relative uncertainty of less than 1% in the concentration range.

Original languageEnglish (US)
Article number5443714
Pages (from-to)1048-1055
Number of pages8
JournalIEEE Sensors Journal
Issue number6
StatePublished - 2010


  • Passive sensing
  • Rinsing monitoring
  • Wafer rinse
  • Water saving
  • Wireless sensing

ASJC Scopus subject areas

  • Instrumentation
  • Electrical and Electronic Engineering


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