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Method for Producing Variable Size Sidewall Images Using a Single Mask

IP.com Disclosure Number: IPCOM000100737D
Original Publication Date: 1990-May-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 3 page(s) / 107K

Publishing Venue

IBM

Related People

Cronin, J: AUTHOR [+2]

Abstract

Flexibility is added to the sidewall image transfer (SIT) process in a range of sizes from the nominal SIT image to zero, and the nominal SIT image to any desired size, all in continuum. Also, a mask step is eliminated.

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Method for Producing Variable Size Sidewall Images Using a Single Mask

       Flexibility is added to the sidewall image transfer (SIT)
process in a range of sizes from the nominal SIT image to zero, and
the nominal SIT image to any desired size, all in continuum. Also, a
mask step is eliminated.

      Sidewall image transfer has been used to produce image sizes
smaller than optical images. By utilizing SIT, two extra masks are
required. One extra mask is used to produce larger than SIT size
images and the other is to remove the "wrap around image" formed on
either side of a support structure. Finally, one spacer thickness
deposition results in one spacer image size and, therefore, a
continuum of image sizes around the normal SIT size is not possible.
A technique is shown for eliminating the extra mask for larger images
as well as allowing a continuum of SIT size images.

      Referring to Fig. 1, a chemical vapor deposition (CVD) film of
thickness Y2 is deposited over two different height structures, Y1
and Y3, respectively. After a reactive ion etch (RIE) step is
performed just to end point, the resultant spacer slope shown by
dotted line 1 and the spacer bottom image "X1" is the same for both
structures, Y1 and Y3. However, after more over etching indicated by
dotted lines 2 and 3, the spacer bottom images change on the smaller
structure, i.e., "X2" and "X3", while the taller structure Y1 is
insensitive to over etching, as shown by the vertical dotted line
forming a constant spacer image "X1".

      Referring to Fig. 2, the figure is separated into three groups,
each generating a different range of continuum of image sizes. Group
1 consists of varying height images of minimum "X" width or less than
"X" size. The varying heights are produced by using a "grey level
mask".  Through one exposure, varying image "heights" can be
produced. Since there is a relation between the original image height
and the bottom image of the spacer, as discussed earlier, a continuum
of images is produced from the original spacer thickness "X" to near
zero sizes.  After these spacers are defined, the...