Extreme ultraviolet lithography reaches 5 nm resolution

Extreme ultraviolet (EUV) lithography is the leading lithography technique in CMOS mass production, moving towards the sub-10 nm half-pitch (HP) regime with the ongoing development of the next generation high-numerical aperture (high-NA) EUV scanners. Hitherto, EUV interference lithography (EUV-IL) utilizing transmission gratings has been a powerful patterning tool for the early development of EUV resists and related processes, playing a key role in exploring and pushing the boundaries of photon-based lithography. However, achieving pattering with HPs well below 10 nm using this method presents significant challenges. In response, our study introduces a novel EUV-IL setup that employs mirror-based technology and circumvents the limitations of diffraction efficiency towards the diffraction limit that is inherent in conventional grating-based approaches. We present line/space patterning of HSQ resist down to HP 5 nm using the standard EUV wavelength 13.5 nm, and the compatibility of the tool with shorter wavelengths beyond EUV. The mirror-based interference lithography tool paves the way towards the ultimate photon-based resolution at EUV wavelengths and beyond. This advancement is vital for scientific and industrial research, addressing the increasingly challenging needs of nanoscience and technology and future technology nodes of CMOS manufacturing in the few-nanometer HP regime

Monatomic phase change memory

Phase change memory has been developed into a mature technology capable of storing information in a fast and non-volatile way, with potential for neuromorphic computing applications. However, its future impact in electronics depends crucially on how the materials at the core of this technology adapt to the requirements arising from continued scaling towards higher device densities. A common strategy to finetune the properties of phase change memory materials, reaching reasonable thermal stability in optical data storage, relies on mixing precise amounts of different dopants, resulting often in quaternary or even more complicated compounds. Here we show how the simplest material imaginable, a single element (in this case, antimony), can become a valid alternative when confined in extremely small volumes. This compositional simplification eliminates problems related to unwanted deviations from the optimized stoichiometry in the switching volume, which become increasingly pressing when devices are aggressively miniaturized. Removing compositional optimization issues may allow one to capitalize on nanosize effects in information storage

Development and characterization of resistive switching memory devices (ReRAM)

129 σ.Στα πλαίσια της εκπόνησης της διπλωματικής μου εργασίας και ταυτόχρονα της πρακτικής μου άσκησης, αναπτύχθηκαν διατάξεις μεταβαλλόμενης αγωγιμότητας που μπορούν να λειτουργήσουν ως στοιχεία μη-πτητικών ηλεκτρονικών μνημών. Κάθε διάταξη είναι μια δομή ΜΙΜ (μέταλλο – ημιαγωγός – μέταλλο), κατασκευασμένη από λεπτά υμένια χρυσού και οξειδίου του τιτανίου, φτωχότερου σε οξυγόνο (TiOx) σε σχέση με το στοιχειομετρικό. Η χαρακτηριστική ιδιότητα του οξειδίου είναι ότι υπό κατάλληλες συνθήκες μπορεί να αλλάξει την αγωγιμότητα του έως και ένα εκατομμύριο φορές. Αν και δεν είναι ακόμα ξεκάθαρο γιατί συμβαίνει αυτό, πιστεύεται ότι οι οπές οξυγόνου μέσα στο πλέγμα του οξειδίου μετακινούνται με την εφαρμογή κατάλληλης τάσης στα άκρα του και δημιουργούνται αγώγιμοι δρόμοι μεταλλικού χαρακτήρα. Η συγκέντρωση και η κατανομή των οπών Ο2- στο οξείδιο είναι μια κατασκευαστική παράμετρος και υπάρχει συγκεκριμένη τιμή τους που βελτιστοποιεί το φαινόμενο της μεταβαλλόμενης αγωγιμότητας. Με τη βοήθεια ηλεκτρικών μεθόδων χαρακτηρισμού ερευνάται η καταλληλότερη “συνταγή” για την ανάπτυξη τους. Η εξάρτηση της επίδοσης του οξειδίου ως μνήμη από τη συγκέντρωση οπών Ο2- στο πλέγμα καθώς και η εξάρτηση της από το πάχος ενός λεπτού υμενίου Ti, που διαδραμάτισε το ρόλο του ηλεκτροδίου της ανόδου, απασχόλησε την παρούσα μελέτη. Κατασκευάστηκαν χαρακτηριστικές καμπύλες ρεύματος τάσης (DC characterization) και μελετήθηκε η αντοχή (endurance) κάθε στοιχείου μνήμης σε επανειλημμένους κύκλους “εγγραφής” και “διαγραφής”. Εξετάστηκε η δυναμική απόκριση της μνήμης σε παλμική λειτουργία, καθώς και η ικανότητά της να διατηρεί την αποθηκευμένη πληροφορία στο πέρασμα του χρόνου (retention). Οι μετρήσεις έδειξαν ικανοποιητικό παράθυρο μνήμης (ποσοτικοποίηση της διάκρισης ανάμεσα σε δύο καταστάσεις που μπορεί να βρεθεί μια μνήμη), τόσο στη συνεχή όσο και στην παλμική λειτουργία, με τη διάταξη να μπορεί να μεταβαίνει μεταξύ περισσοτέρων του ενός διακριτών επίπεδων αγωγιμότητας (multilevel switching). Τα αποτελέσματα καθιστούν τα οξείδια ανταγωνιστικά για τις εφαρμογές σε νέας γενιάς κυκλώματα μνήμης. Μελέτη της επιφάνειας των οξειδίων με τη χρήση μικροσκοπίας ατομικών δυνάμεων (AFM) έδειξε πως τα οξείδια μας είναι ποιοτικά, ομοιόμορφα και με χαμηλή τραχύτητα. Επιπλέον το οξείδιο λειτούργησε ως μνήμη στη νανοκλίμακα με τη χρήση αγώγιμης μικροσκοπίας ατομικών δυνάμεων (C-AFM), δίνοντας αποτελέσματα που μας επιτρέπουν να εκτιμήσουμε ομαλή λειτουργία των οξειδίων ως στοιχεία μνημών πολύ μεγάλης πυκνότητας ολοκλήρωσης, απαραίτητης για οποιαδήποτε υποψήφια νέα τεχνολογία στο χώρο της βιομηχανίας μνημών.As part of the preparation of my diploma thesis and at the same time my internship, devices with varying conductivity were developed in order to function as non-volatile memory elements. Each device comprises a structure of Metal-Insulator-Metal (MIM) and consists of thin films of gold (Au) and titanium dioxide with low oxygen content (TiO2-x) in contrast with the stoichiometric film (TiO2). The very special ability of these types of oxides is that, under proper conditions, their conductivity can be altered as much as 106 times. Although it is not clear why this phenomenon takes place, it is argued that oxygen vacancies within the lattice of oxide are displaced under the application of proper voltage bias and thus conducting channels of metallic nature are formed. The density and distribution of oxygen vacancies within the oxide is strongly related with the fabrication details and there is a specific value of their concentration and distribution that optimizes the switching effect. With the assistance of electrical characterization techniques the quality of different fabrication procedures is investigated. The impact of oxygen vacancies on the performance of the memory cell as well as the implication of a thin Ti layer above the oxide film, which served the role of top electrode in our devices, were systematically examined in this study. In addition, DC characteristics of current-voltage bias were recorded during one or consecutive cycles function. The dynamical response under pulse function was monitored in combination with the retention capability. Measurements divulged satisfying memory window (OFF/ON ratio), in both quasi-static and pulse function mode, where multiple switching states were demonstrated. The outcome renders our oxide films attractive for new generation memory circuits. Detailed surface analysis of our oxides through Conductive-Atomic Force Microscopy (C-AFM) disclosed the high quality of them, revealing their low roughness. Furthermore, the surface mapping of the measured current gives a great amount of information of the memory element in nanoscale area, which is of great importance for any potential candidate technology in the industrial memory area.Ιάσων Γ. Γιαννόπουλο

In-Memory Database Query

In recent years, several in-memory logic primitives were proposed where bit-wise logical operations are performed in memory by exploiting the physical attributes of memristive devices organized in a crossbar array. However, a convincing real-world application for in-memory logic and its experimental validation are still lacking. Herein, the application of database query where a database is stored in an array of binary memristive devices is presented. The queries are formulated in terms of bulk bit-wise operations and are executed in memory by exploiting Kirchhoff's current summation law. The concept is experimentally demonstrated by executing error-free queries on a small 4x8 selector-less phase-change memory crossbar. The impact of crossbar size, resistance of routing wires, and interdevice variability on the accuracy of the logical operations are studied through numerical and circuit-level simulations. Finally, a system for cascaded query is proposed that combines the in-memory logic with conventional digital logic and its functionality is verified on a healthcare-related database. It is estimated that an 11-step long query is executed in 36ns, consuming 560 mu W, thus achieving an energy efficiency of 166TOPS/W.ISSN:2640-456

Extreme ultraviolet lithography reaches 5 nm resolution

Extreme ultraviolet (EUV) lithography is the leading lithography technique in CMOS mass production, moving towards the sub-10 nm half-pitch (HP) regime with the ongoing development of the next generation high-numerical aperture (high-NA) EUV scanners. Hitherto, EUV interference lithography (EUV-IL) utilizing transmission gratings has been a powerful patterning tool for the early development of EUV resists and related processes, playing a key role in exploring and pushing the boundaries of photon-based lithography. However, achieving pattering with HPs well below 10 nm using this method presents significant challenges. In response, our study introduces a novel EUV-IL setup that employs mirror-based technology and circumvents the limitations of diffraction efficiency towards the diffraction limit that is inherent in conventional grating-based approaches. We present line/space patterning of HSQ resist down to HP 5 nm using the standard EUV wavelength 13.5 nm, and the compatibility of the tool with shorter wavelengths beyond EUV. The mirror-based interference lithography tool paves the way towards the ultimate photon-based resolution at EUV wavelengths and beyond. This advancement is vital for scientific and industrial research, addressing the increasingly challenging needs of nanoscience and technology and future technology nodes of CMOS manufacturing in the few-nanometer HP regime