hydrophilicity of exposed portions  206a  (in other words, the  polymers become more hydrophobic), decreasing solubility  of exposed portions  206a  to a developer. Alternatively, in  some implementations, the exposure process and/or the PEB  process increase hydrophilicity of exposed portions  206a  (in  other words, the polymers become more hydrophilic),  increasing solubility of exposed portions  206a  to the <level- aper.  In some implementations, R$_{1 }$is n-propyl and R$_{2 }$ is isopropyl,  such that organic solvent  214  is represented by formula (IV):  US 10,520,820 B2  9  In some implementations, R$_{1 }$ and R$_{2 }$ are selected to balance  hydrophobicity and hydrophilicity of NTD developer  210,  such that organic solvent  214  has a log P value greater than  1.82. For example, in some implementations, R$_{1 }$ and R$_{2 }$ are  not polar functional groups. In some implementations, NTD  developer  210  further includes another organic solvent, such  as n-butyl acetate (n-BA), such that NTD developer  210  includes co-solvents. A ratio between organic solvent  214  and n-BA is determined by characteristics of resist layer  206,  such as desired solubility, molecular weights of the polymer,  PAG, and/or other resist components, molecular weight  dispersity, polarity of monomers, monomer sequences, other  suitable resist characteristics, or combinations thereof. In  some implementations, NTD developer  210  further includes  additives, surfactants, and/or other suitable developer com- ponents.  In FIG.  2D,  a developing process is performed on resist  layer  206,  thereby forming patterned resist layer  206’.  In the  depicted embodiment, a negative tone development (NTD)  process is performed to remove unexposed portions  206b  of  resist layer  206.  For example, an NTD developer  210  is  applied to resist layer  206  that dissolves unexposed portions  206b,  leaving patterned resist layer  206’  having opening(s)  212  defined therein between exposed portions  206a  (collec› tively referred to as a resist pattern). In some implementa› tions, a rinsing process is performed after the developing  process, for example, to remove any residue and/or particles  from workpiece  200.  In some implementations, a post› development baking (PDB) process is performed, for  example, to ensure structural stability of patterned resist  layer  206’.  NTD developer  210  includes a new and improved com› position that overcomes RLS tradeoff barriers discussed  herein, particularly those associated with EUV lithography,  providing improved patterning fidelity. NTD developer  210  includes an organic solvent  214  that is an ester acetate  derivative having a log P value greater than 1.82. For  example, organic solvent  214  is represented by R$_{1}$COOR$_{2}$ ,  where R$_{1 }$ and R$_{2 }$ are hydrocarbon chains having four or less  carbon atoms. In some implementations, organic solvent  214  is represented by formula (I):  Organic solvent  214  increases hydrophobicity of NTD  developer  210,  such that NTD developer  210  unable to  penetrate ( or minimally penetrate) exposed portions  206a,  yet is hydrophilic enough to effectively penetrate and  remove unexposed portions  206b,  resulting in minimal (to  no) swelling of exposed portions  206a.  Opening(s)  212  are  thus defined by relatively smooth edges and/or sidewalls of  exposed portions  206a,  such that the resist pattern of pat› terned resist layer  206’  exhibits minimal LER/LWR and  improved resist contrast, significantly enhancing lithogra› phy resolution. The improved LER/LWR and resist contrast  is achieved at lower exposure dosages, such as those achiev- able by current EUV technologies. NTD developer  210  having organic solvent  214  thus improves sensitivity of  resist layer  206  without sacrificing resolution and/or LERI  LWR, thereby breaking the RLS tradeoff. Accordingly, NTD  developer  210  is particularly useful for EUV lithography, the  target lithography technology for sub-10 nanometer IC  fabrication, which typically requires higher sensitivity. Dif› ferent embodiments disclosed herein offer different advan- tages and no particular advantage is necessarily required in  all embodiments.  where Ri, R$_{2}$ , or both R 1  and R$_{2 }$ are propyl functional  groups. In some implementations, R$_{1 }$ is ethyl and R$_{2 }$ is  2-methylpropyl (also referred to as isobutyl), such that  organic solvent  214  is represented by the formula (II):  In some implementations, R$_{1 }$is isopropyl and R$_{2 }$ is n-propyl,  such that organic solvent  214  is represented by formula (III):  NTD developer  210  performs superior to conventional  NTD developers including n-BA solvents and/or derivatives  thereof, which dissolve resist materials too easily and/or  penetrate exposed portions of resist materials (thereby  increasing LER and/or pattern deformation). FIG.  3  includes  a graph  250  having EUV contrast curves, such as an EUV  contrast curve  260  and an EUV contrast curve  270,  for resist  layers developed using different developers according to  various aspects of the present disclosure. EUV contrast  curves correlate post-development remaining resist thick- ness  (%) (y-axis) as a function of a logarithm of exposure  dose (Eop) (in millijoules (mJ)) (x-axis). EUV contrast  curve  260  and EUV contrast curve  270  were obtained by  exposing a resist layer, such as resist layer  206,  to various  exposure doses of EUV radiation and developing the resist  layer using different developers. EUV contrast curve  260  corresponds with a resist layer developed by conventional  NTD developers, such as n-BA solvents and/or derivatives  thereof, having organic solvents with log P values greater  than 1.82. EUV contrast curve  270  corresponds with a resist  layer developed by NTD developers disclosed herein, such  as NTD developer  210  including organic solvent  214  having  (IV)  10  (I)  (II)  (III) 