Method to Produce Sizes in Openings in Photo Images Smaller Than Lithographic Minimum Size
Original Publication Date: 1986-Aug-01
Included in the Prior Art Database: 2005-Mar-09
Publishing Venue
IBM
Related People
Abstract
By means of the addition of a well-controlled thickness of material to sidewalls on a minimum lithographic size opening, well-controlled smaller openings are formed. An example of a useful application is described wherein recessed oxide (ROX) pad openings are formed which are, e.g., 0.4 micron smaller than the minimum achievable lithographic image size. The material, e.g., polycrystalline silicon (Poly-Si), is added to sidewalls of openings by first depositing the Poly-Si by a conformal deposition process, e.g., chemical vapor deposition (CVD), and then using an anisotropic etching process, e.g., reactive ion etching (RIE), to remove the CVD Poly-Si from regions coplanar to the substrate. Referring to the figure, conventional processing is used to create pad oxide (SiO2) 4 and pad nitride (Si3N4) 6 on a silicon substrate 2.
Method to Produce Sizes in Openings in Photo Images Smaller Than Lithographic Minimum Size
By means of the addition of a well-controlled thickness of material to sidewalls
on a minimum lithographic size opening, well-controlled smaller openings are
formed. An example of a useful application is described wherein recessed oxide
(ROX) pad openings are formed which are, e.g., 0.4 micron smaller than the
minimum achievable lithographic image size. The material, e.g., polycrystalline
silicon (Poly-Si), is added to sidewalls of openings by first depositing the Poly-Si
by a conformal deposition process, e.g., chemical vapor deposition (CVD), and
then using an anisotropic etching process, e.g., reactive ion etching (RIE), to
remove the CVD Poly-Si from regions coplanar to the substrate. Referring to the
figure, conventional processing is used to create pad oxide (SiO2) 4 and pad
nitride (Si3N4) 6 on a silicon substrate 2. Next, a layer of Poly-Si 8 is deposited
to a thickness t suitable to act as a mask in a boron field ion implantation process
(t>0.3 micron), photo-patterned and etched to form holes of minimum lithographic
size m. A layer 10 of Poly-Si is conformally deposited by CVD to a thickness of
0.2 micron (um). This layer 10 is then removed from all regions coplanar with the
substrate 2 by RIE, leaving edge spacers of 0.2 um thickness on sidewalls of
openings originally m wide, thus producing openings 0.4 micron smaller than
minimum lithographic size m. The field...