Charged-particle-beam microlithography methods exhibiting reduced coulomb effects

A method for performing charged-particle-beam (CPB) microlithography of a pattern, defined on a reticle, to a sensitive substrate, the method comprising:

• defining the pattern on a segmented reticle that is either a scattering-stencil reticle or a scattering-membrane reticle;
• individually illuminating selected regions of the reticle with a CPB illumination beam to produce a corresponding patterned beam;
• blocking at least most of the charged particles in the patterned beam that are highly scattered during passage through the reticle from reaching the sensitive substrate, and focusing charged particles that are not scattered and that are weakly scattered during passage through the reticle as a projected image on the sensitive substrate;
• and
• with respect to regions of the reticle defining critical features of the pattern, reducing a beam current of the patterned beam reaching the sensitive substrate, relative to a beam current actually passing through the reticle, to 50% or less by performing the steps of (a) establishing the pattern, as defined on the reticle, as a normal-tone pattern or as an inverted-tone pattern;
• and (b) establishing the resist on the substrate as a positive or negative resist.

A method for performing charged-particle-beam (CPB) microlithography of a pattern, defined on a reticle, to a sensitive substrate, the method comprising:

• defining the pattern on a segmented reticle that is either a scattering-stencil reticle or a scattering-membrane reticle, the reticle being divided into multiple subfields each defining a respective portion of the pattern;
• individually illuminating the subfields with a CPB illumination beam to produce a corresponding patterned beam directed to the sensitive substrate;
• blocking at least most of the charged particles in the patterned beam that are highly scattered during passage through the reticle from reaching the sensitive substrate, and focusing charged particles that are not scattered and that are weakly scattered during passage through the reticle as a projected image on the sensitive substrate;
• stitching together the subfield images on the substrate so as to imprint a complete pattern on the substrate;
• for exposing the pattern, reducing a beam current of the patterned beam reaching the sensitive substrate, relative to a beam current actually passing through the reticle, to 50% or less by performing the steps of (a) establishing the pattern, as defined on the reticle, as a normal-tone pattern or as an inverted-tone pattern;
• and (b) establishing the resist on the substrate as a positive or negative resist;
• and
• according to an exposure rule, defining the pattern in a normal tone on the reticle and using a negative resist on the substrate whenever (ηmax+ηmin)/2≦50%, wherein η is a mean pattern-element density for the entire pattern, ηmax is a maximum pattern-element density for each subfield, and ηmin is a minimum pattern-element density for each subfield, and defining the pattern in an inverted tone on the reticle and using a positive resist on the substrate whenever (ηmax+ηmin)/2>50%.

A method for performing charged-particle-beam (CPB) microlithography of a pattern, defined on a reticle, to a sensitive substrate, the method comprising:

• defining the pattern on a segmented reticle that is either a scattering-stencil reticle or a scattering-membrane reticle, the reticle being divided into multiple subfields each defining a respective portion of the pattern;
• individually illuminating the subfields with a CPB illumination beam to produce a corresponding patterned beam directed to the sensitive substrate;
• blocking at least most of the charged particles in the patterned beam that are highly scattered during passage through the reticle from reaching the sensitive substrate, and focusing charged particles that are not scattered and that are weakly scattered during passage through the reticle as a projected image on the sensitive substrate;
• stitching together the subfield images on the substrate so as to imprint a complete pattern on the substrate;
• with respect to subfields defining critical features of the pattern, reducing a beam current of the patterned beam reaching the sensitive substrate, relative to a beam current actually passing through the reticle, to 50% or less by performing the steps of (a) establishing the pattern, as defined on the reticle, as a normal-tone pattern or as an inverted-tone pattern;
• and (b) establishing the resist on the substrate as a positive or negative resist;
• and
• defining the pattern in a normal tone on the reticle and using a negative resist on the substrate whenever (ηcmax+ηcmin)/2≦50%, wherein ηc is a mean pattern-element density for all subfields of the pattern that include critical features, ηcmax is a maximum pattern-element density for each subfield that includes critical features, and ηcmin is a minimum pattern-element density for each subfield that includes critical features, and defining the pattern in an inverted tone on the reticle and using a positive resist on the substrate whenever (ηcmax+ηcmin)/2>50%.