Scott M. Lewis

In this paper, we report on a novel metal organic photoresist based on heterometallic rings that was designed for electron beam and extreme ultraviolet lithography. From initial electron beam lithography studies, the resist performance demonstrated excellent resolution of 15 nm half-pitch (HP) and a silicon dry etch selectivity of 100:1 but at the expense of sensitivity. To improve sensitivity, a 3D Monte Carlo simulation was employed that utilizes a secondary electron generation model. The simulation suggested that the sensitivity could be dramatically improved while maintaining high resolution by incorporating HgCl₂ species into the resist molecular design. This considerably improved the resist sensitivity without losing the high resolution, where it was determined that the resist sensitivity was increased by a factor of 1.6 and 1.94 while demonstrating a resolution of 15 nm and 16 nm HP when exposed with electrons and EUV radiation respectively. Using x-ray photoelectron spectroscopy measurements, we show that after exposure to the electron beam the resist materials are transformed into a metal oxyfluoride and this is why the resist demonstrates high resistance to silicon dry etch conditions achieving a selectivity of 60:1 at a resolution of 15 nm HP.

Metal-organic materials such as [NH2(CH2-CH-CH2)(2)][Cr7NiF8(Pivalate)(16)] can act as negative tone resists for electron beam lithography (EBL) with high-resolution patterning of sub-40 nanometer pitch while exhibiting ultrahigh dry etch selectivities >100:1 and giving line dose exposures >11,000 pC/cm. It is clear that the resist sensitivity is too low to be used to manufacture the latest nanoscale photomasks that are suitable for extreme ultraviolet lithography. Therefore, the focus of this work here is to improve the sensitivity of this resist while maintaining its resolution and dry etch selectivity. Using our latest Monte Carlo simulation called Excalibur, we predict that the sensitivity would increase by a factor of 1.4 when the nickel atom is substituted by a cadmium atom. EBL studies showed an excellent agreement with the simulation, and plasma etching studies demonstrated that this did not affect the dry etch performance of the resist which remains very good with a selectively of ca. 99:1 for the etching of silicon at these resolutions with a low sensitivity of 7995 pC/cm.

A new class of electron bean negative tone resist materials has been developed based on heterometallic rings. The initial resist performance demonstrates a resolution of 15 nm half‐pitch but at the expense of a low sensitivity. To improve sensitivity a 3D Monte Carlo simulation is used that utilizes a secondary and Auger electron generation model. The simulation suggests that the sensitivity can be dramatically improved while maintaining high resolution by incorporating appropriate chemical functionality around the metal–organic core. The new resists designs based on the simulation have the increased sensitivity expected and illustrate the value of the simulation approach.

Field emission devices are promising candidates to replace silicon FinFETs as next-generation nanoelectronic components. For these devices to be adopted, nanoscale field emitters with nanoscale gaps between them need to be fabricated, requiring the transfer of e.g. sub-10 nm patterns with sub-20 nm pitch into substrates like silicon and tungsten. New resist materials must therefore be developed that exhibit the properties of sub-10 nm resolution and high dry etch resistance. A negative tone, metal–organic resist is presented here. It can be patterned to produce sub-10 nm features when exposed with helium ion beam lithography at line doses on the order of 10s of pC/cm. The resist was used to create 5 nm wide, continuous, discrete lines spaced on a 16 nm pitch in silicon, and 6 nm wide lines on 18 nm pitch in tungsten, with line edge roughness of 3 nm. After the lithographic exposure, the resist demonstrates high resistance to silicon and tungsten dry etch conditions (SF6 and C4F8 plasma), allowing the pattern to be transferred into the underlying substrates. The resist’s etch selectivity for silicon and tungsten was measured to be 6.2:1 and 5.6:1, respectively; this allowed 3-4 nm thick resist films to yield structures that were 21 and 19 nm tall, respectively, while both maintained sub-10 nm width on sub-20 nm pitch.

A new resist material for electron beam lithography has been created that is based on a supramolecular assembly. Initial studies revealed that with this supramolecular approach, high‐resolution structures can be written that show unprecedented selectivity when exposed to etching conditions involving plasmas.

A new resist material for electron beam lithography has been created that is based on a supramolecular assembly. Initial studies revealed that with this supramolecular approach, high‐resolution structures can be written that show unprecedented selectivity when exposed to etching conditions involving plasmas.