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Low Dielectric Constant Inorganic Insulators for BEOL and Packaging Applications

IP.com Disclosure Number: IPCOM000114203D
Original Publication Date: 1994-Nov-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 61K

Publishing Venue

IBM

Related People

Chandrashekhar, GV: AUTHOR [+2]

Abstract

New, very low dielectric constant insulators would be desirable in bipolar and CMOS devices to minimize circuit wiring delays. In an investigation of new insulator systems having structures isomorphic with those of quartz (SiO&sub2.) as a replacement for SiO&sub2. or polyimide in BEOL and packaging applications, we have found that boron phosphate, BPO&sub4., exhibits an unusually low dielectric constant and other desirable properties for such applications. Indeed, BPO&sub4. may be a potential substitute for glass-ceramic substrates for high-speed electronic circuitry.

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Low Dielectric Constant Inorganic Insulators for BEOL and Packaging
Applications

      New, very low dielectric constant insulators would be desirable
in bipolar and CMOS devices to minimize circuit wiring delays.  In an
investigation of new insulator systems having structures isomorphic
with those of quartz (SiO&sub2.) as a replacement for SiO&sub2.  or
polyimide in BEOL and packaging applications, we have found that
boron phosphate, BPO&sub4., exhibits an unusually low dielectric
constant and other desirable properties for such applications.
Indeed, BPO&sub4.  may be a potential substitute for glass-ceramic
substrates for high-speed electronic circuitry.

      The valence electronic configuration of BPO&sub4.  is
iso-electronic with that of SiO&sub2.  and under ambient temperature
and pressure its structure is that of tetragonal crystobalite.  We
have prepared BPO&sub4.  as a single phase material by reacting
H&sub3.BO&sub3.  and H&sub3.PO&sub4.  at room temperature and drying
the resulting gelatinous solid at 110ºC.  Preliminary experiments
on a sintered pellet of approximately 85%  bulk density, obtained by
heating the dried solid to 1200ºC, gave a dielectric constant of
2.5-2.6 and a dissipation factor of 0.002 at 1 MHz.  While the
dielectric constant will increase somewhat with further
densification, it is significantly lower than that of quartz (4.0)
and cordierite glass-ceramics (4,5), and compares quite favorably
with those of polyimides (2.5 to 3.0 and higher).  The material does
not appear to degrade or react with the ambient atmosphere.  Its
die...