The development of Chemically Amplified Resists (CARs) for Extreme Ultra-Violet Lithography (EUVL) requires unique molecular and macromolecular design considerations. The combination of photon-induced variation effect coupled with material and processing variabilities makes stochastic consequences in EUV resist significantly more severe than that in ArF resist. Among the other factors, conversion of the scarce number of absorbed EUV photons into imaging events is directly modulated by acid generation quantum yield. In this study, we measure the EUV acid generation efficiency of different Photoacid Generators (PAGs). Our results show that in addition to PAG electronic properties, other structural-driven PAG properties can have a significant impact on resist sensitivity. In a complementary part of this study, we have measured PAG acid generation efficiency under EUV exposure in newly designed polymer matrixes. Such polymers comprise high absorption EUV elements and EUV-specific sensitizers. Insights into the effect of the polymer matrix on EUV acid generation quantum yield are presented.
Conventional doping of crystalline Si via ion implantation results in a stochastic distribution of doped regions in the x-y plane along with relatively poor control over penetration depth of dopant atoms. As the gate dimensions get to 10 nm, the related device parameters also need to be scaled down to maintain electrical activity. Thus highly doped abrupt, ultra-shallow junctions are imperative for source-drain contacts to realize sub-10 nm transistors. Uniform ultra-shallow junctions can be achieved via monolayer doping, wherein thermal diffusion of a self-limiting monolayer of dopant atomcontaining organic on Si surface yields sub-5 nm junctions. We have extended the use of organic dopant molecules in the monolayer doping technique to introduce a new class of spin-on polymer dopants. In effect, these new spin-on dopants offer a hybrid between the monolayer doping technique and traditional inorganic spin-on dopants. We have been able to uniformly introduce p- and n-type dopants with doping efficiencies comparable to the monolayer doping technique. Control over junction depth can be easily achieved via optimizing annealing temperature and time. Concurrently, sequestering the dopant precursors within the cores of block copolymer micelles allows us to achieve precise control over the spatial positions of dopant atoms in all three dimensions owing to the high periodicity of block copolymer domains on the 10-100 nm length scale.
The use of multilayer processes in advanced ArF patterning schemes continues to increase as device critical dimensions shrink. In a multilayer stack, underlayer materials play a critical role in terms of gap fill, planarization and etch resistance to enable high resolution and high aspect ratio patterning. The emerging quadlayer imaging process requires a unique spin on carbon (SOC) layer with high thermal stability to withstand subsequent deposition of an inorganic hard mask layer, commonly deposited via chemical vapor deposition (CVD). The thermal stability requirement associated with CVD compatibility largely limits the options of organic materials, which mostly decompose in the 300-450°C range. Thermal shrinkage and coefficient of thermal expansion (CTE) differences between layers are other key considerations in designing a high temperature stable, CVD compatible SOC material. Furthermore, the SOC polymer resin must be compatible with solvents and spin on products commonly used in the FAB. This paper highlights the development of a novel CVD compatible HT-SOC platform with excellent thermal stability (>500°C) and good FAB drain line compatibility. In addition, this polyaromatic SOC platform shows various improvements compared to traditional Novolacbased SOC, including reduced shrinkage, good gap fill, improved planarization, and low defectivity. Robust formulation design, high quality raw materials, and advanced metal removal technique synergistically enabled manufacturing of multigallon HT-SOC product with high quality. Application specific versions are available for more demanding planarization requirement and applications that require good adhesion to metal substrate. In addition, a newly developed method for quantitative measurement of long-range planarization was used to validate new material designs aimed at improving planarization.
As devices become ever smaller and more sophisticated, there is also a general need for creating high quality defect-free thin coatings of polymers on 3-dimensional wafer topography, for example, for shrinkage of the size of trench openings. To address this challenge, we developed a spin-on polymer brush material, which comprises of a dopant moiety with a universal adhesive dopamine end group. We demonstrate that the polymer coating is highly conformal and free of pinhole defects, even when only a few nm thick, or when coated over high aspect ratio over 200 nm deep trench topography. Our investigations demonstrate that the dopamine end group enables stable sub-10 nm thick conformal coatings on three-dimensional surfaces.
Furthermore, on acute 3-dimensional semiconductor topography, the creation of highly doped abrupt, ultra-shallow junctions with three-dimensional control are essential for successful source-drain contacts. In consideration of this need, we extended the above polymer brush concept further by incorporating a suitable implant dopant atom, such as boron, into the monomer structure. After conformal coating and a subsequent rapid thermal annealing process, the dopant atom is driven into the semiconductor substrate underneath the polymer film. This is potentially very useful for uniform all-around doping of 3-dimensional topography such as FinFETs or Nanowire-FETs. A high dopant dosage on silicon substrate with appropriate shallow implant characteristics was demonstrated for the end-functionalized dopant polymer brush, highlighting one of the promising applications of such conformal coatings.
A trilayer stack of spin-on-carbon (SOC), silicon anti-reflective coating (SiARC) and photoresist (PR) is often used to enable high resolution implant layers for integrated circuit manufacturing. Damage to substrates from SiARC removal using dry etching or aqueous hydrogen fluoride has increased the demand for innovative SiARC materials for implant lithography process. Wet strippable SiARCs (WS-SiARCs) capable of stripping under mild conditions such as SC1 (ammonium hydroxide/hydrogen peroxide/water) while maintaining key performance metrics of standard SiARCs is highly desirable. Minimizing the formation of Si-O-Si linkages by introducing organic crosslink sites was effective to impart SC1 solubility particularly after O2 dry etching. Incorporation of acidic groups onto the crosslinking site further improved SC1 solubility. A new siloxane polymer architecture that has SC1 active functionality in the polymer backbone was developed to further enhance SC1 solubility. A new SiARC formulation based on the new siloxane polymer achieved equivalent lithographic performances to a classic SiARC and SC1 strip rate >240Å/min under a relatively low concentration SC1 condition such as ammonium hydroxide/hydrogen peroxide/water=1/1/40.