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Browse Prior Art Database

Performance Enhancement and Size Reduction in Radio Frequency Identification Tags

IP.com Disclosure Number: IPCOM000119111D
Original Publication Date: 1997-Nov-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Brady, MJ: AUTHOR [+2]

Abstract

Devices built on silicon wafers have parasitic capacitances and resistances. The parasitics are not desirable because they introduce losses, reduce the quality factors, and limit the highest speed that the devices can be operated. The degradation in device characteristics caused by the parasitics becomes more significant at higher frequencies and may prohibit the devices to function properly at radio frequencies, such as 915 MHz and 2.45 GHz.

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This is the abbreviated version, containing approximately 84% of the total text.

Performance Enhancement and Size Reduction in Radio Frequency Identification
Tags

      Devices built on silicon wafers have parasitic capacitances and
resistances.  The parasitics are not desirable because they introduce
losses, reduce the quality factors, and limit the highest speed that
the devices can be operated.  The degradation in device
characteristics caused by the parasitics becomes more significant at
higher frequencies  and may prohibit the devices to function properly
at radio frequencies,  such as 915 MHz and 2.45 GHz.

      The parasitics can be found in commonly seen devices such as
Schottky diodes, capacitors, spiral inductors, transistors, and even
in contact pads and bumps.  As an example, the parasitics between the
planar coil in a spiral inductor and the conductive silicon substrate
can be so large that the inductor typically has a very poor Q and low
self-resonant frequency and may even become capacitive.  In order to
reduce the parasitics at Radio Frequency (RF), an "excavation"
technology has been applied to spiral inductors by several groups of
researchers around the world.  In this technology, the the silicon
beneath the spiral  was removed (by etching), and the air gap so
created provided a low-loss  low-dielectric-constant medium that
dramatically reduced the parasitics.

      This disclosure proposes applying the excavation technology to
other RF devices.  More specifically, the excavation technique is
applied to the pads...