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Low Temperature Grain Growth and Epitaxial Alignment of Polysilicon Using Thin Aluminum Layers

IP.com Disclosure Number: IPCOM000105306D
Original Publication Date: 1993-Jul-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 2 page(s) / 73K

Publishing Venue

IBM

Related People

Brodsky, SB: AUTHOR [+6]

Abstract

Disclosed is a controlled method for forming epitaxial Si from polysilicon and promoting grain growth in polysilicon at low temperature. This approach uses Al metallization in contact with polysilicon to promote recrystallization during annealing. Potential applications include thin film transistors, personalized resistors, low resistance polysilicon studs and gate conductors, and local interconnects able to withstand high temperature processing.

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Low Temperature Grain Growth and Epitaxial Alignment of Polysilicon Using Thin Aluminum Layers

      Disclosed is a controlled method for forming epitaxial Si from
polysilicon and promoting grain growth in polysilicon at low
temperature.  This approach uses Al metallization in contact with
polysilicon to promote recrystallization during annealing.  Potential
applications include thin film transistors, personalized resistors,
low resistance polysilicon studs and gate conductors, and local
interconnects able to withstand high temperature processing.

      Solid phase epitaxy regrowth of polycrystalline Si on
crystalline Si and grain growth in polysilicon are usually thought of
as high-temperature processes (typically requiring temperatures in
the range of 900ºC or higher).  Therefore it is usually hard
to obtain a large grain size (and accompanying low sheet rho and high
mobilities) in a practical integrated device process due to thermal
cycle constraints.  Large grain polysilicon is required in a number
of applications where one would like to minimize the number of grain
boundaries (e.g., for TFT) or where it is desirable to minimize the
poly sheet rho.

      We propose using thin Al layers together with a capping layer
of dielectric such as SiO&sub2.  for producing large grain
polysilicon or epitaxial Si at low temperatures (500ºC).  In
order to achieve a larger poly grain size at lower temperatures, it
has been shown that solid phase epitaxy of amorphous Si on
crystalline Si and grain growth in polysilicon are both enhanced by
the presence of metal layers [1,2] because the metal provides a fast
diffusion path for the moving species.  In previous work with Al on
polysilicon [2], the Al film was thick (hundreds of nm) and
unconstrained, so that large Si grains grow in the Al.  While this
approach increases the grain size of the polysilicon, it also results
in very rough films with uneven...