Method for reducing, by a factor or 2.sup.-N, the minimum masking pitch of a photolithographic process
First Claim
1. A method for manufacturing an integrated circuit, comprising the following sequence of steps:
- (a) forming a primary mask strip, said mask strip having a first feature width;
(b) transforming the primary mask strip into a mandrel strip, said mandrel strip having substantially vertical sidewalls and a second feature width that is less than said first feature width;
(c) forming stringer strips on the sidewalls of said mandrel strip, each of said stringer strips having a third feature width; and
(d) removing the mandrel strip from between the stringer strips.
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Accused Products
Abstract
The process starts with a primary mask, which may be characterized as a pattern of parallel, photoresist strips having substantially vertical edges, each having a minimum feature width F, and being separated from neighboring strips by a minimum space width which is also approximately equal to F. From this primary mask, a set of expendable mandrel strips is created either directly or indirectly. The set of mandrel strips may be characterized as a pattern of parallel strips, each having a feature width of F/2, and with neighboring strips being spaced from one another by a space width equal to 3/2F. A conformal stringer layer is then deposited. The stringer layer material is selected such that it may be etched with a high degree of selectivity with regard to both the mandrel strips and an underlying layer which will ultimately be patterned using a resultant, reduced-pitch mask. The stringer layer is then anisotropically etched to the point where the top of each mandrel strip is exposed. The mandrel strips are then removed with an appropriate etch. A pattern of stringer strips remains which can then be used as a half-pitch mask to pattern the underlying layer. This process may also be repeated, starting with the half-pitch mask and creating a quarter-pitch mask, etc. As can be seen, this technique permits a reduction in the minimum pitch of the primary mask by a factor of 2-N (where N is an integer 1, 2, 3, . . . ).
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Citations
32 Claims
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1. A method for manufacturing an integrated circuit, comprising the following sequence of steps:
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(a) forming a primary mask strip, said mask strip having a first feature width; (b) transforming the primary mask strip into a mandrel strip, said mandrel strip having substantially vertical sidewalls and a second feature width that is less than said first feature width; (c) forming stringer strips on the sidewalls of said mandrel strip, each of said stringer strips having a third feature width; and (d) removing the mandrel strip from between the stringer strips. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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11. A method for manufacturing an integrated circuit, comprising the following sequence of steps:
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(a) forming a primary mask pattern, said mask pattern including a plurality of parallel mask strips, each mask strip having a first feature width, and each mask strip being separated from each adjacent strip by a first space width; (b) transforming the primary mask pattern into a pattern of parallel mandrel strips, each mandrel strip having substantially vertical sidewalls, a second feature width that is less than said first feature width, and being separated from each adjacent mandrel strip by a second space width that is less than said first space width; (c) forming stringer strips on the sidewalls of each mandrel strip, each of said stringer strips having a third feature width; and (d) removing the mandrel strips to leave a pattern of stringer strips, each stringer strip being separated from each adjacent stringer strip by a third space width.
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23. A method for halving the pitch of a primary mask, said method comprising the following sequence of steps:
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(a) forming a primary mask pattern on an underlying layer, said primary mask pattern including a plurality of parallel photoresist strips of substantially identical feature width, said photoresist strips being equidistantly spaced from one another and having a feature width to space width ratio of substantially 1;
1;(b) forming a pattern of parallel, equidistantly-spaced mandrel strips on a substrate, said mandrel strips having substantially identical feature widths, substantially vertical sidewalls, a pitch that is identical to the pitch of the primary pattern, and a feature width to space width ratio of substantially 1;
3;(c) depositing a conformal, partially-expendable stringer layer on exposed regions of the substrate and on the top and sidewalls of each mandrel strip, said partially-expendable stringer layer having a thickness that is substantially equal to the width of each mandrel strip; (d) anisotropically etching the partially-expendable stringer layer so as to form stringer strips on the sidewalls of each mandrel strip, and expose not only the top of each mandrel strip, but also regions of the substrate between each pair of stringer strip-widened mandrel strip; and (e) removing the mandrel strips to leave a pattern of stringer strips, said pattern of stringer strips having half the pitch of the primary mask pattern. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31, 32)
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Specification