Previously, fundamental evaluations of the Extreme Ultra Violet (EUV) lithography process have been conducted using the CLEAN TRACK ACT (TM) 12 coater/developer with the ASML EUV Alpha Demo Tool (ADT) at imec.([1]) ([2]) In that work, we confirmed the basic process sensitivities for the critical dimension (CD) and defectivity with EUV resists. Ultimate resolution improvements were examined with TBAH and FIRM (TM) Extreme. Moving forward with this work, the latest inline cluster is evaluated using the ASML NXE:3100 pre-production EUV scanner and the CLEAN TRACK (TM) LITHIUS Pro (TM) -EUV coater/developer. The imec standard EUV baseline process has been evaluated for manufacturability of CD uniformity control based on half pitch (HP) 27nm and ultimate resolution studies focusing on HP 22nm. With regards to the progress of the improvement for EUV processing, we confirmed the effectiveness of several novel concepts: FIRM (TM) Extreme10 showed increase in ultimate resolution and improvement in line width roughness (LWR) and process window; Tokyo Electron LTD. (TEL) smoothing process for roughness reduction showed 17% improvement for line and space (L/S) patterns; and finally the new dispense method reduced patterned wafer defectivity by over 50%.

Extreme ultraviolet (EUV) - lithography at a wavelength around 13.5 nm is considered as the most promising successor of optical projection lithography. This paper reviews simulation models for EUV lithography. Resist model parameters are calibrated with experimental data. The models are applied for the investigation of the impact of mask multilayer defects on the lithographic process.

In order to further understand the processing sensitivities of the EUV resist process, TEL and imec have continued their collaborative efforts. For this work, TEL has delivered and installed the state of the art, CLEAN TRACK (TM) LITHIUS Pro (TM) -EUV coater/developer to the newly expanded imec 300mm cleanroom in Leuven, Belgium. The exposures detailed in this investigation were performed off-line to the ASML EUV Alpha Demo Tool (ADT) as well as on the in-line ADT cluster with CLEAN TRACK (TM) ACT (TM) 12 coater/developer. As EUV feature sizes are reduced, is it apparent that there is a need for more precise processing control, as can be demonstrated in the LITHIUS Pro (TM) -EUV. In previous work from this collaboration(1), initial investigations from the ACT (TM) 12 work showed reasonable results; however, certainly hardware and processing improvements are necessary for manufacturing quality processing performance. This work continues the investigation into CDU and defectivity performance, as well as improvements to the process with novel techniques such as advanced defect reduction (ADR), pattern collapse mitigation with FIRM (TM) Extreme and resolution improvement with tetrabutylammoniumhydroxide (TBAH).

As lithographic technology is moving from single pattern immersion processing for 45nm node to double patterning for the next generation and onward to EUV processing, TEL is committed to understanding the fundamentals and improving our technology to enable customers to meet roadmap expectations. With regards to immersion and double patterning technology, TEL has presented a wide variety of technologies to advance the processing capability of our customers. With regards to EUV technology, we have previously presented work for simulation and modeling of an EUV resist system(1) in order to further our understanding of the differences between resist performance from previous platforms and currently available EUV resists. As it's currently unknown which direction resist suppliers will take with regards to platform in order to surpass the current limitations in resolution, roughness and sensitivity trade off's, we need to consider the implications of such kinds of novel platforms to track processing capabilities. In this work, we evaluated two of the more promising materials, to determine processing sensitivities necessary for the development of new hardware and process applications. This paper details the initial study complete for understanding the track process parameters such as dissolution characteristics and the impact of film hydrophobicity. Fundamental processing knowledge from 193 and 248nm technology is applied to understand where processing deviates from known sensitivities and will require more development efforts.

In this paper, the experiences on full field EUVL lithography are reviewed. Besides the imaging performance of the EUV ADT at IMEC, also the progress in resists and reticles are discussed and compared to the production requirements for EUV lithography.

The ASML extreme ultraviolet lithography (EUV) alpha demo tool is a 0.25NA fully functional lithography tool with a field size of 26x33 mm(2), enabling process development for sub-40-nm technology. Two exposure tools are installed at customer facilities, and are equipped with a Sri discharge source. In this paper we present data measured at intermediate focus of the Sri source-collector module. We also present performance data from both exposure tools, show the latest results of resist exposures including excellent 32-nm half pitch dense staggered and aligned contact hole images, and present the highlights of the first demonstration of an electrically functional full field device with one of the layers made using EUVL in ASML's alpha demo tool.

There still remain three major technological lithography options for high volume manufacturing at the 32nm half pitch node: 193nm immersion lithography with high index materials, enabling NA>1.6; 193nm double patterning and EUV lithography. In this paper the pros and cons of these three options will be discussed. Particular interest will be paid to the consequences of the final choice on the resist technology. High index 193nm immersion lithography also requires high index resist materials, which are under development but still far removed from the target refractive index and absorbance specifications not to mention lithographical performance. For double patterning the pitch may be relaxed, but the resists still need to be able to print very narrow lines and/or trenches. Moreover, it would be preferred for the resists to support pattern or image freezing techniques in order to step away from the litho-etch-litho-etch approach and make double patterning more cost effective. For EUV the resist materials need to meet very aggressive sensitivity specifications. In itself this is possible, but it is difficult to simultaneously maintain performance in terms of resolution and line width roughness. A new parameter (KLUP) for assessing resist performance in terms of these three performance criteria will be introduced.

ASML has built and shipped to The College of Nanoscale Science and Engineering of the University at Albany (CNSE) and IMEC two full field step-and-scan exposure tools for extreme ultraviolet lithography. These tools, known as Alpha Demo Tools (ADT), will be used for process development and to set the foundation for the commercialization of this technology. In this paper we will present results from the set-up and integration of both ADT systems, status of resist and reticles for EUV, and the plans for using these tools at the two research centers. We will also present the first resist images from one of the tools at the customer site, and demonstrate 32nm half-pitch dense lines/spaces printing as well as 32nm dense contact hole printing.

The influence of partial fluorination on the lithographic performance of photoresists based on ( meth)acrylate terpolymers containing polyhedral oligomeric silsesquioxane (POSS) pendant groups is investigated in bilayer schemes for 193 nm lithography. For the first time the capability of POSS-functionalized resists for standard lithographic processing, including use of standard developer (0.26 N tetramethylammonium hydroxide) and industrial processing equipment is demonstrated. The optimized resists formulated exhibited high sensitivity (< 10 mJ/cm(2)) and potential for resolution performance comparable to mature 193 nm materials. The role of the fluorinated acid as a component in the terpolymer composition was crucial to the homogeneity of the resist material and its lithographic performance. Also, a photoacid generator (PAG) study revealed that the use of a highly hydrophobic PAG containing organic anion with a long fluorinated chain in the resist formulation improved further the homogeneity of the material and its lithographic performance. The adhesion of the highly fluorinated materials to the substrate is influenced by the type of polymeric underlayer used, whereas best results were obtained on a hard baked novolac polymer.

Linewidth control in the 0.25μm 0.18μm range will be one of the biggest challenges for future optical lithography. Various parameters contribute to CD variations: stepper parameters, lens errors, mask imperfections, resist processing, wafer topography, proximity effects and operator errors. The goal of this paper is to elaborate on the most important contributors to CD variations. Linewidth control is studied directly, characterised by the 36 variation of the CD spread. Our investigations are based on simulations and on experimental work. CD control for 0.25μm applications is compared for four resist strategies: negative tone resist with TAR, negative tone resist on BARC, positive tone resist on BARC and top surface imaging (TSI) in combination with dry development. Proximity correction is taken into account. Best results are obtained with the negative tone process on BARC and with TSI. Concerning CD-control for 0.18μm devices, a feasibility study is carried out, based on simulations. NA and a optimisation will be required for sufficient CD control, as well as proximity correction on the mask. This feasibility study is illustrated with various experimental results obtained using TSI (Desire process).

Linewidth control in the 0.25μm-0.18μm range will be one of the biggest challenges for future optical lithography. Various parameters contribute to CD variations: stepper parameters, lens errors, mask imperfections, resist processing, wafer topography, proximity effects and operator errors. The goal of this paper is to elaborate on the most important contributors to CD variations. Linewidth control is studied directly, characterised by the 3σ variation of the CD spread. Our investigations are based on simulations and on experimental work. CD control for 0.25μm applications is compared for four resist strategies: negative tone resist with TAR, negative tone resist on BARC, positive tone resist on BARC and top surface imaging (TSI) in combination with dry development. Proximity correction is taken into account. Best results are obtained with the negative tone process on BARC and with TSI. Concerning CD-control for 0.18μm devices, a feasibility study is carried out, based on simulations. NA and σ optimisation will be required for sufficient CD control, as well as proximity correction on the mask. This feasibility study is illustrated with various experimental results obtained using TSI (Desire process).

Most surface imaging resist processes are based on selective incorporation of silicon during silylation, followed by dry development of the resist. The dry development is an important parameter in the resist processing, because it will influence the resist profile and the sensitivity to residues, and, hence, the process latitude. For the DESIRE process, the silicon diffusion profile will be more steep by applying a so called two step dry development, which will result in a steeper resist profile and less residue. For several dry development schemes, the resist profile and the sensitivity to residue are investigated. The etch selectivities corresponding to the various development processes are measured, since they play a major role in the resulting lithographic performance. Further, the useful silylation window with respect to silicon incorporation and DUV induced crosslinking is determined for each type of development. Finally, the resolution and the process latitudes resulting from the different development processes are compared.