Metal oxide or metal nitride films are used as hard mask materials in the semiconductor lithography processes due to their excellent etch resistances against the plasma etches. Chemical vapor deposition (CVD) or atomic layer deposition (ALD) techniques are usually used to deposit the metal containing materials on substrates or underlying films, which uses specialized equipment and can lead to high cost-of-ownership and low throughput.The present paper describes formation and functional properties of novel metal oxide hard masks by simple solution spin coating process. These stable metal oxide formulations containing significant amount of Ti, W, Hf, Zr and Al possess good etch selectivity and therefore good pattern transfer capability. The metal oxide films can be removed by commonly used wet chemicals in the fab environment such as TMAH developer, solvents or other oxidizing agents.The hard mask material absorbs DUV wavelengths and hence can be used as a spin-on inorganic or hybrid antireflective coating to control substrate reflectivity. Some metal hard masks are also developed for via or trench filling applications for electronic devices as high K materials. The research demonstrated that these metal oxide hard masks are compatible with litho track and etch processing without concern of metal contamination. They can, therefore be integrated as replacements of CVD or ALD metal, metal oxide, metal nitride or spin-on silicon-containing hard mask films in 193 nm or EUV processes. This paper discusses coating, optical, filling, etch and wet removal properties the spin-on metal oxide formulations. In addition, a new potential application in self-aligned quadruple patterning cut process for advanced technology nodes is also described.
Hard masks play an important role in pattern transfer to the desired substrate in the semiconductor lithography processes. Organic and inorganic type hard masks are used. While most organic hard masks such as carbon and siloxane type are solution spin coated, inorganic type hard masks such as SiON and SiN are either chemical vapor deposited (CVD) or atomic layer deposited (ALD). Future generation of lithography processes require hard masks with higher resistance to fluorinated plasma and materials that can be easily wet stripped after pattern transfer process to prevent dry etch damage to the substrate underneath.The present paper describes formation and functional properties of novel metal oxide hard masks by simple solution spin coating process. These novel metal oxide hard masks offer good etch selectivity and can easily be partially or fully wet strippable using commonly used chemicals in the FABs. The spin coatable composition has good long-term shelf life and pot life stability based on solution LPC analysis and wafer defect studies. The hard mask material absorbs DUV wavelengths and can be used as a spin-on inorganic or hybrid antireflective coating to control substrate reflectivity under DUV exposure of photoresist. At the same time they are transparent at 500-700nm for alignment mark identification and can be spin coatable up to 450nm thickness with good film quality. Some of these metal-containing materials can be used as an underlayer in EUV lithography to significantly enhance sensitivity of the photoresist. Specific metal hard masks are also developed for via or trench filling applications in IRT processes. The materials have shown good coating and lithography performance with a film thicknesses as low as 10 nm under ArF dry or immersion conditions.
EUV lithography continues to be developed as a technology for sub-30nm and especially sub-20nm pattern imaging in the semiconductor industry. To achieve the desired photoresist resolution, line width roughness and sensitivity (RLS) performance for such fine feature patterns, multilayer materials are almost certainly needed to define the overall lithography process. EUV underlayer (EBL) materials with high EUV photon absorption (EPA) unit can improve resist performance in areas such as sensitivity, imaging capability, dissolution contrast, resolution and process window. In this paper, we report more detailed studies on our new generation of EBL materials, showing enhanced integrated EUV performance including reduction of LWR. One advanced EBL material tested has incorporated metal components, and shows sensitivity improvement as well as high etch selectivity, and can be used as hard mask for next generation pattern imaging.
New model1'2 using the concept of gel layer was recently presented that aimed to provide a theoretical interpretation for experimental data of dissolution behavior to control the lithographic performance of the photoresist. The dependence of the dissolution rate of phenolic polymer on the aqueous base concentration and molecular weight of resin can be analytically described by mathematical modeling considering the formation of gel layer, which is formed by the entry of aqueous base and deprotonation of some of the phenol group. The new polymer dissolution model is based on the suggested mechanism that the diffusion of base and deprotonation reaction of the phenolic group of polymer take place simultaneously through a gel layer. The fundamental equation, which is derived from the concept of gel layer, correctly fits experimental data for aqueous base concentration and molecular weight dependence of dissolution rate of phenolic polymer. In addition, the model can predict the experimentally critical minimum base concentration below which dissolution is no longer observed.As a result, the mathematical expression by this approach offers a fully quantitative and analytical understanding of the dissolution rate.
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