Hydrogen silsesquioxane

Hydrogen silsesquioxane(s) (HSQ, H-SiO_x, T^H_n, H-resin) are inorganic compounds with the empirical formula [HSiO_3/2]_n. The cubic H₈Si₈O₁₂ (T^H₈) is used as the visual representation for HSQ.^{[clarification needed]} T^H₈, T^H₁₀, T^H₁₂, and T^H₁₄ have been characterized by elemental analysis, gas chromatography–mass spectroscopy (GC-MS), IR spectroscopy, and NMR spectroscopy.^[1]

Hydrogen silsesquioxane (R = H).

High purity semiconductor-grade HSQ has been investigated as a negative resist in photolithography and electron-beam (e-beam) lithography.^[2] HSQ is commonly delivered in methyl isobutyl ketone (MIBK) and can be used to form 0.01–2 μm films on substrates/wafers. When exposed to electrons or extreme ultraviolet radiation (EUV), HSQ cross-links via hydrogen evolution concomitant with Si-O bond crosslinking. Recently, the possibility of crosslinking HSQ using ultrashort laser pulses through multiphoton absorption and its application to 3D printing of silica glass have been demonstrated.^[3][4] Sufficiently dosed and exposed regions form a low dielectric constant (low-k) Si rich oxide that is chemically resistant/insoluble towards developers, such as tetramethylammonium hydroxide (TMAH). Sub-10 nm patterning is achievable with HSQ. The nanoscale patterning capabilities and low-k of the Si rich oxide produced is potentially of broad scope of nano applications and devices.^[5]

HSQ has been available as 1 and 6% (wt%) MIBK solutions from Dow Inc. (Formally Dow Corning), called XR-1541-001 and XR-1541-006, respectively. HSQ in MIBK has a short shelf life. Alternatively, Applied Quantum Materials Inc. (AQM) produces HSQ with a longer shelf life.^[6][7] AQM HSQ solutions are available in the United States from DisChem, Inc. EM Resist Ltd (UK) also manufactures and supplies HSQ worldwide both as powder and in solution.

References

1. Agaskar, P. A.; Day, V. W.; Klemperer, W. G. (1987-09-01). "A new route to trimethylsilylated spherosilicates. Synthesis and structure of [Si12O18](OSiMe3)12, D3h-[Si14O21](OSiMe3)14, and C2v-[Si14O21](OSiMe3)14". Journal of the American Chemical Society. 109 (18): 5554–5556. doi:10.1021/ja00252a058. ISSN 0002-7863.
2. Namatsu, H.; Yamaguchi, T.; Nagase, M.; Yamazaki, K.; Kurihara, K. (1998-03-01). "Nano-patterning of a hydrogen silsesquioxane resist with reduced linewidth fluctuations". Microelectronic Engineering. International Conference on Micro- and Nanofarbication. 41–42: 331–334. doi:10.1016/S0167-9317(98)00076-8. ISSN 0167-9317.
3. Jin, Feng; Liu, Jie; Zhao, Yuan-Yuan; Dong, Xian-Zi; Zheng, Mei-Ling; Duan, Xuan-Ming (2022-03-15). "λ/30 inorganic features achieved by multi-photon 3D lithography". Nature Communications. 13 (1): 1357. Bibcode:2022NatCo..13.1357J. doi:10.1038/s41467-022-29036-7. ISSN 2041-1723. PMC 8924217. PMID 35292637.
4. Huang, Po-Han; Laakso, Miku; Edinger, Pierre; Hartwig, Oliver; Duesberg, Georg S.; Lai, Lee-Lun; Mayer, Joachim; Nyman, Johan; Errando-Herranz, Carlos; Stemme, Göran; Gylfason, Kristinn B.; Niklaus, Frank (2023-06-07). "Three-dimensional printing of silica glass with sub-micrometer resolution". Nature Communications. 14 (1): 3305. Bibcode:2023NatCo..14.3305H. doi:10.1038/s41467-023-38996-3. ISSN 2041-1723. PMC 10244462. PMID 37280208.
5. Chen, Yifang (2015-03-05). "Nanofabrication by electron beam lithography and its applications: A review". Microelectronic Engineering. 135: 57–72. doi:10.1016/j.mee.2015.02.042. ISSN 0167-9317.
6. Shen, Jiashi; Aydinoglu, Ferhat; Soltani, Mohammad; Cui, Bo (2019-03-01). "E-beam lithography using dry powder resist of hydrogen silsesquioxane having long shelf life". Journal of Vacuum Science & Technology B. 37 (2): 021601. Bibcode:2019JVSTB..37b1601S. doi:10.1116/1.5079657. ISSN 2166-2746. S2CID 104333826.
7. Jiashi, Shen (2018-09-28). E-beam Lithography using Dry Powder HSQ Resist Having Long Shelf Life and Nanogap Electrode Fabrication (Thesis).

Further reading

• Chen, Huiping; Tecklenburg, Ron E. (October 2006). "Characterization of low and intermediate molecular weight hydrogen silsesquioxanes by mass spectrometry". Journal of the American Society for Mass Spectrometry. 17 (10): 1438–1441. Bibcode:2006JASMS..17.1438C. doi:10.1016/j.jasms.2006.06.010. ISSN 1044-0305. PMID 16872839. S2CID 3674845.
• Frye, Cecil L.; Collins, Ward T. (1970-09-01). "Oligomeric silsesquioxanes, (HSiO3/2)n". Journal of the American Chemical Society. 92 (19): 5586–5588. doi:10.1021/ja00722a009. ISSN 0002-7863.