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Roughness has always been a key detractor of the optical losses within the silicon photonics devices. With scaling at 300mm wafer, there is an introduction of new tools such immersion lithography scanner, OPC technique that can help to drive furthermore the optical losses reduction. This study will detail the work done on characterizing multiple steps of the process (Lithography, Etch, Annealing) and using roughness tools such LER (Line Edge Roughness), LWR (Line Width Roughness) and finally PSD (Power Spectral Density) to understand the main detractor of the optical losses at each step. These data will be extracted using SEM imaging from VeritySEM 6i.

Current Mueller polarimeters, with either spectral or angular resolution, feature high enough precision and speed to be suitable for many demanding applications, with specific advantages over conventional spectroscopic ellipsometry (SE). Due to the simultaneous determination of depolarization, birefringence and diattenuation Mueller polarimetry (MP) can open new fields in surface and thin film characterization techniques with new and very powerful intrinsic analyses of roughness and/or anisotropy. For more conventional applications, such as scatterometry (i.e. the determination of the shape of periodic structures from optical measurements, mostly used in microelectronics), MP may overpass SE in terms of systematic errors and/or measurement spot size, as discussed from two examples. However, numerical simulations remain a key point to take full advantage of MP capabilities for the new challenges emerging in nanometrology.

Proximity Effects in electron beam lithography impact feature dimensions, pattern fidelity and uniformity. These effects are addressed using a mathematical model representing the radial exposure intensity distribution induced by a point electron source, commonly named as the Point Spread Function (PSF). PSF models are usually employed for predicting and compensating for effects up to 15μm. It is well known that there are also some process related phenomena that impact pattern uniformity that have a longer range, namely CMP effects, fogging, etc. Performing proximity effects corrections can result in lengthy run times as file size and pattern densities continue to increase exponentially per technology node. Running corrections for extreme long range phenomena becomes computational and file size prohibitive. Nevertheless, since extreme long range may reach up several millimeters, and new technology nodes require a high level of precision, a strategy for predicting and compensating these phenomena is crucial. In this paper a set of test patterns are presented in order to verify and calibrate the so called extreme long range effects in the electron beam lithography. Moreover, a strategy to compensate for extreme long range effects based on the pattern density is presented. Since the evaluation is based on a density map instead of the actual patterns, the computational effort is feasible. The proposed method may be performed off-line (in contrast to machine standard in-line correction). The advantage of employing off-line compensation relies on enhancing the employ of dose and/or geometry modulation. This strategy also has the advantage of being completely decoupled from other e-beam writer’s internal corrections (like Fogging Effect Correction - FEC).

The use of optical metrology techniques for process control is now widespread. These techniques are fast and nondestructive, allowing higher throughputs than non-optical techniques like electron microscopies or AFM. We present here new developments using complete Mueller polarimetry in the back focal plane of a microscope objective to characterize overlay for microelectronic industry. Based on fundamental symmetries in the physics of periodic structures and polarized light and redundancies in the angle-resolved Mueller images we define estimators which vary linearly with the overlay. As a result, overlay measurement is sensitive to both the direction and sign of the overlay, and it does not require any detailed modeling of the target structures, provided two independent targets with known overlay values are available in close locations on the wafer. Realistic simulations on optimized structures suggest that accuracies in the order of 1 or 2 nm or better should be achievable. Moreover, with high NA objectives the proposed technique can be implemented with targets with lateral sizes as small as a few μm. Experimental results of both grating line profiles and overlay determinations will be presented. The samples, elaborated at LETI, have been accurately characterized by optical imaging AIM techniques and state-of-the-art AFM. The latest developments on the device itself as well as the advantages, possibilities and limitations of this new metrology technique will be discussed.

Angle resolved Mueller polarimetry implemented as polarimetric imaging of the back focal plane of a high NA microscope objective has already demonstrated a good potential for CD metrology 1 . In this paper we present the experimental and numerical results which indicate that this technique may also be competitive for measurements of the overlay error / between two gratings at different levels. Series of samples of superimposed gratings with well controlled overlay errors have been manufactured and measured with the angle resolved Mueller polarimeter. The overlay targets were 20 µm wide. When overlay error / = 0 the absolute value of Mueller matrix elements is invariant by matrix transposition. This symmetry breaks down when G z 0. As a result, we can define the following overlay estimator matrix: ( _0 _ _0 _ t . The simulations show that matrix element E 14 is the most sensitive to the overlay error. In the experiments the scalar estimator of E 14 was defined by averaging the pixel values over specifically chosen mask. The scalar estimator is found to vary essentially linearly with G for the overlay values up to 50 nm. Our technique allows entering quite small overlay marks (down to 5 µm wide). Th e only one target measuremen t is needed for each overlay direction. The actual overlay value can be determined without detailed simulation of the structure provided the two calibrated overlay structures are available for each direction. Keywords: Overlay metrology, Mueller matrix polarimetry, polarimetric imaging, conoscopic mode imaging.

Molecular resist have potential interest for low CDs and LERs required in future lithography technology. The lithographic ability of one of them is exposed in this study, by e-beam and by EUV-IL. Work on process condition is described and leads to dense-lines resolution down to 32.5nm for.

International audience; Angle resolved Mueller polarimetry implemented as polarimetric imaging of a back focal plane of a high NA microscope objective has already demonstrated a good potential for CD metrology. Here we present the experimental and numerical results indicating that this technique may also be competitive for the measurements of overlay error delta. A series of samples of superimposed gratings with well controlled overlay errors have been manufactured and measured with the angle resolved Mueller polarimeter. The overlay targets were 20-mu m wide. When the overlay error is delta is equal to 0, absolute values of elements of real 4x4 Mueller matrix M are invariant by matrix transposition. Otherwise this symmetry breaks down. Consequently, we define the following overlay estimator matrix as E = |M| - |M|(t). The simulations show that matrix element E-14 is the most sensitive to the overlay error. The scalar estimator of E-14 was calculated by averaging the pixel values over a specifically chosen mask. This estimator is found to vary linearly with d for overlay values up to 50 nm. Our technique allows entering small overlay marks (down to 5-mu m wide). Only one target measurement is needed for each overlay direction. The actual overlay value can be determined without detailed simulation of the structure provided two calibrated overlay structures are available for each direction.

A technique to probe defects buried inside extreme ultraviolet (EUV) masks has been implemented using a dark-field microscopy detection setup. Specific samples have been fabricated to evaluate the sensitivity of this technique. They consist of silicon oxide gratings of a few nanometers height, coated with 40 layer pairs of molybdenum-silicon. We observed images with a good contrast on samples with defects as low as 3 nm. However, the imaging mechanism of scanning dark-field microscopy is not linear and can produce image distortions. Conditions of correct imaging have been analyzed, and simulations have been performed that show good agreement with the experimental data. This work opens the way for a better understanding of the capability of at-wavelength inspection technique for EUV mask.