Current Status of Inorganic Nanoparticle Photoresists

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1 Prof. Christopher K. ber Department of Materials Science and Engineering, Cornell University, Ithaca NY Current Status of Inorganic Nanoparticle Photoresists Markos Trikeriotis, Marie Krysak, Yeon Sook Chung, Christine uyang, Emmanuel Giannelis (Cornell) Brian Cardineau, Robert Brainard (CNSE, Albany) CRNELL Mark Neisser, Kyoungyong Cho (Sematech)

2 Presentation verview Introduction to inorganic photoresists Lithographic performance highlights: EUV patterning Etching and pattern transfer Versatile resist platform: Dual-tone capability Alternative formulations EUV absorbance optimization CRNELL

3 Inorganic Photoresist Platform Why Inorganic Photoresist? High resolution: High aspect ratio Pattern collapse X Thinner film: Improved patterning ü Poor pattern transfer X High etch-resistance photoresist: Improved pattern transfer ü Advantages: Nanoparticles are soluble in PGMEA and other common coating solvents. Choice of the organic ligands can alter the photoresist chemistry: both positive tone and negative tone patterning. EUV absorbance, sensitivity and etch resistance can be fine-tuned by changing the combination and ratios of metal oxide, organic ligand and photoactive compound CRNELL

4 Resist Formulation Spin coating solvent: PGMEA HfMAA or ZrMAA: 5-10% w/v propylene glycol monomethyl ether acetate Photoactive compound: 1-10% w/w relative to nanoparticle mass Me Me Photoinitiator or PAG dimethoxy phenyl acetophenone CRNELL

5 Absorption optimization Film absorption depends on atomic composition and density µ = N A ρ MW i x iσ α i rganic/inorganic hybrid Inorganic: Hf 2 Zr 2 high density materials Hf has higher absorbance than Zr at 13.5 nm rganic: Lower density Photo absorption crosssection (cm 2 /mol) Zr Hf Absorption optimization: Hf:Zr ratio rganic content film density Atomic Number CRNELL

6 EUV Lithography Highest EUV sensitivity reported to date! SuMMIT analysis: CD = 26.1 ± 0.11 nm LWR = 6.0 ± 0.10 nm LER = 3.8 ± 0.07 nm SuMMIT analysis: CD = 21.5 ± 0.58 nm LWR = 9.0 ± 0.18 nm LER = 5.6 ± 0.18 nm Zr-MAA + PAG Dose: 4.2 mj/cm 2 Half pitch 34nm 32nm 30nm 28nm Zr-MAA + PAG Dose: 16.5 mj/cm 2 CRNELL

7 Etch Resistance / Pattern Transfer Etch rate comparison of PHST and Hf-MAA resist 2 plasma treatment has no detrimental effect on pattern transfer 200 Film thickness (nm) nm/sec 0.17 nm/sec PHST HfMAA SF 6 / 2 pattern transfer Time (sec) HfMAA has 25 times better etch resistance than PHST CF 4 pattern transfer CRNELL

8 E-beam and 193i Lithography HfMAA + DPAP 193 dry, negative tone, 150nm HfMAA + DPAP E-beam, negative tone HfMAA + DPAP 193 immersion, negative tone, 40nm CRNELL

9 Inorganic Photoresist Platform Metal oxide nanoparticles with organic surface ligands Many possible combinations of inorganic cores, organic ligands and photoactive compounds Photoactive compound Inorganic cores to date: Zr 2 or Hf 2, other metal oxides can be used rganic shell: Carboxylic and sulfonic acids bind strongly. Tailored ligands. Photoactive compounds: Photoradical initiator or PAG CRNELL

10 First Hypothesized Mechanism Negative tone: Crosslink MAA via radical mechanism Positive tone unlikely Hf 2 H H Hf 2 H H H Hf 2 Hf 2 Hf 2 Hf 2 CRNELL

11 Dual-Tone Photoresist Dual-tone photoresist: Dual-Tone Capability The same Hf or Zr based films can be patterned on both tones only by changing the postexposure processing (+) HfMAA (-) (+) ZrMAA (-) CRNELL

12 Alternative Cores and Ligands H H Hf 2 H H H ü Dual-tone ü EUV ü E-beam, 193, DUV Alternative ligands: HfMAA H H Zr 2 H H H ü Dual-tone ü EUV ü E-beam, DUV ZrMAA H H Hf 2 H H H ü Dual-tone ü E-beam, DUV HfIBA CRNELL

13 Synthesis and Characterization Film FT-IR of Hf-MAA Transmittance (%) Wavenumber (cm-1) Particle size - DLS 2-3 nm Hf- MAA Zr- MAA Number (%) Particle diameter (nm) rganic content TGA Controlled MAA concentration CRNELL

14 Negative tone Not CAR Mechanism rganic alcohol developer, no PEB Photoinitiator or photoacid generator aids ligand crosslinking IR also suggests a change in the bonds corresponding to the binding ligands Positive tone Aq. base developer, PEB needed Solubility of unexposed regions is changed with PEB IR of Hf-MAA with 5 wt% PAG Difference between unexposed and exposed films Transmittance (%) Wavenumber (cm-1) CRNELL

15 Summary Highly sensitive, high resolution EUV resist based on Hf-xide and Zr-xide Excellent etch resistance Both negative (expected) and positive (unexpected) tone New non-car mechanism for pattern formation ther cores and ligands possible and this will lead to further improvements CRNELL