Real time scatterometry: a new metrology for in situ microelectronics process control

In situ and real time control of the different process steps in semiconductor device manufacturing becomes a critical challenge, especially for the lithography and plasma etching processes. Real time scatterometry is among the few solutions able to meet the requirement for in line monitoring. In this paper we demonstrate that real time scatterometry can be used as a real time monitoring technique during the resist trimming process. For validation purposes the real time scatterometry measurements are compared with 3D Atomic Force Microscopy measurements made in the same process conditions. The agreement between both is excellent

Real-time profile shape reconstruction using dynamic scatterometry

International audienceIn-line process control in microelectronic manufacturing requires real-time and non-invasive monitoring techniques. Among the different metrology techniques, the scatterometry, based on the ellipsometric signatures (i.e stokes coefficients vs. wavelengths) of light scattered by a patterned structures, seems to be well adapted to address this kind of problem. For instance, the shape evolution of a grating in real time during etch processing can be monitored. Traditionally, the direct problem of defining the shape and computing the signature is dealt with modal methods. However, the inverse problem can not be solved as easily. Different classes of algorithms have been introduced (evolutionary, simplex), but the method of library searching is more commonly used in industry. The main limit of this method is the acquisition time of data for different wavelengths. Then, a lack of data can leads to the method failure and several database patterns can be matched to the experimental data. In this article, a technique for real time reconstruction of grating shape variation using dynamic scatterometry is presented. The different tools to realize this reconstruction, such as Modal Method by Fourier Expansion, regularization technique and mostly the specific soft and hardware architecture are also developed. Results of a dynamic experiments will illustrated these presentations

Adaptation de la méthode PEEC à la représentation électrique des structures de l'électronique de puissance

There will be no getting away from spécifie CAD tool for circuit designers in power electronic. Prototype test stages hâve the same need. This work deals with this Computing prototype aspect. The electromagnetic environment of power component is studied, and more precisely problems coming from cabling structures. As a first step, parasitic inductance are studied for spécifie cabling structures: the busbar technology. This study is carried out to insert cabling electrical model in circuit software. A method to balance current in paralleled component is also presented. In a second part, the parasitic capacitance aspect is taken into account. The aim of this study is to find an efficient method to determinate parasitic capacitance of complex system. Différent software are so tested. The method that we will use is based on PEEC method. This method is validated with some measurements.Les outils informatiques deviennent incontournables pour les concepteurs de circuits en électronique de puissance. Les étapes de tests sur prototypes n'échappent pas à cette règle. Le travail présenté dans ce manuscrit s'inscrit dans cet axe de " prototypage informatique ". Il met en avant l'étude de l'environnement électromagnétique des composants de puissance. Plus précisément, les imperfections dues au câblage seront étudiées. Dans un premier temps, les inductances parasites sont étudiées pour des structures particulières de câblage : la technologie busbar. Cette étude s'inscrit dans une volonté d'intégrer le câblage comme un composant à part entière dans les logiciels. Une méthode permettant de s'affranchir des déséquilibres en courant dans les composants mis en parallèles est également présentée. Dans une deuxième partie, l'aspect capacitif est pris en compte. Le but de cette étude est de trouver une méthode rapide et efficace de déterminer les capacités parasites de systèmes complexes. Une comparaison de plusieurs logiciels est donc effectuée. La méthode retenue est une adaptation de la méthode PEEC. Celle-ci est validée par des mesures

Validity of the Diffused Aerial Image Model: an Assessment Based on Multiple Test Cases

Lithography modeling is a very attractive way to predict the critical dimensions of patterned features after lithographic processing. In a previous paper[1], we have presented the assessment of three different simplified resist models (aerial image model, aerial image convolved with fixed gaussian noise and aerial image convolved with variable gaussian noise) by using a systematic comparison between experimental and simulated data. It has been shown that the aerial image convolved with fixed gaussian noise, or "diffused aerial image model" (DAIM), exhibits surprisingly good results of CD prediction for lines @ 193nm: using these datasets, the DAIM appears as a fast and accurate model for CD prediction. This approach allows also an easy run, and because it needs only four adjustable parameters, it avoids the difficult task of resist parameters extraction associated to full resist models, with. In this paper, we enlarge the datasets used for the assessment of the DAIM by considering both lines and contact holes of various sizes printed at different wavelengths. The reference wafers have been printed at 248nm, 193nm and 157 nm. The procedure used to extract the model parameters has been improved and now needs less data to provide acceptable values. We will show that the validity of the DAIM extends well outside the results presented in ref. 1. Experimental data printed using various wavelengths, resists and exposure tools can be simulated accurately with CD prediction error ranging within few percents. It is to be noted that the results that will be presented on contact holes data indicate that the model is valid for 2D features. Finally, a comparison with full resist models shows that the accuracy of DAIM is comparable to more sophisticated and heavier models

Three-dimensional rigorous simulation of EUV defective masks using modal method by Fourier expansion

In Extreme Ultraviolet Lithography, the electromagnetic modelling of the mask allows determining the influence of the mask structure on the electromagnetic field. That makes it possible to take into account the presence of a defect modifying the multi-layer stack1,2. The method used throughout this paper is the MMFE (Modal Method by Fourier Expansion) also known as the RCWA (Rigorous Coupled Wave Analysis). Modal methods allow computing the electromagnetic field just above the EUV mask or the near field. Modal methods are well adapted for EUV mask simulation due to materials and structure size. The previous works performed on 2D simulation with MMFE3 have shown the influence of a defect inside a EUV mask structure. In this article, the method is extended to address 3D structures. The printability of a spherical shaped defect is analyzed depending on the deposition process used. The influence of a 3D defect position regarding the position of a line absorber is also shown

Assessment of different simplified resist models

Resist modeling is an attractive way to predict the critical dimensions of patterned features after lithographic processing. Unfortunately, previous works have shown that model parameters are very difficult to determine and have often a poor range of validity outside the dataset that have been used to generate them [1, 2]. The goal of this work is to assess different simplified resist models using a systematic method. We have studied the accuracy of aerial image model and aerial image plus gaussian noise convolution model. The approach is based on the comparison between simulated and experimental data for periodic lines of various dimensions at various illumination conditions. We also propose a reliable expression for Bossung curves fitting. Using simple physical considerations, the expression has been made very simple and efficient. After a proper setting of the model parameters to the experimental data, mean CD discrepancies between simulation and experiment are as small as 5% and can be 3% for certain feature types. Moreover, we show that simple gaussian noise convolution models can be predictive with the same accuracy. The method for CD prediction is fully described in this paper. Significant improvements have been made in resists modeling over the last several years, but simplified resist models such as "aerial image + gaussian noise " seems to be an effective tool for CD prediction, which remains the major demand of IC manufacturers

Développement des techniques de scatteromètrie en temps réel pour le suivi des procédés de gravure plasma

La scatterométrie dynamique est une technique de métrologie optique basée sur une analyse de la lumière diffractée par un objet, elle fait preuve d'un potentiel remarquable, il s'agit d'une technique non-destructive applicable au contrôle in-situ en temps réel. L'article présente des résultats de l'application de la scatterometrie dynamique pour le contrôle d'un procédé de « resist trimming ». Les mesures obtenues par scatteromètrie sont comparées avec des mesures 3D-AFM obtenues dans les mêmes conditions

Application of PSD for the extraction of programmed line roughness from SAXS

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