由IBM發明的賽道記憶體(Racetrack memories)最近受到加州大學戴維斯分校(UC Davis)研究人員的重視，他們認為透過一種具前景的新材料可望使賽道記憶體成為現實。
UC Davis目前正與半導體研究公司(Semiconductor Research Corporation；SRC)共同合作，期望利用奈米線打造出一種較硬碟(HD)或固態快閃記憶體(flash)更快速、更高容量、更可靠且更低功耗的賽道記憶體。
「當今的趨勢是在電腦中加進固態快閃記憶體，但它比起硬碟更昂貴，」SRC奈米製程科學總監Bob Havemann表示，「但我們能成功地配置這種賽道記憶體，它可帶來更快速度、更低成本、更高容量、更加可靠以及提高能效。」
UC Davis的研究人員們一直致力於研究一種稱為「鑭鍶錳氧」(LSMO；La0.67 Sr0.33 Mn O3)的氧化物及其特性，它具有新穎的磁、電與光學特性。
「我們一直在研究氧化物材料或多鐵性材料，因為這些材料的磁狀態不僅可以透過磁場改變，也會因為電場和光線而變化，」UC-Davis教授Yayoi Takamura表示，「在與SRC合作後，我們一直在構圖打造賽道記憶體所需的幾何圖案──內含凹陷以限制磁疇壁的1維奈米線。」
賽道記憶體的工作原理類似於硬碟，而且它是完全固態的，相較於磁碟在寫入磁頭下旋轉磁疇的方式，賽道記憶體的磁疇沿著由凹陷式奈米線組成的閉合軌道讀寫。奈米線的磁狀態可經由寫入磁頭定位加以改變，從而改變每個凹陷的磁向，然後將沿著奈米線長度編碼的圖案移至下一凹陷，因而以賽道來比喻。
「IBM先前的開發工作是在金屬材料上進行，但我們看好的是複雜的氧化物，並試圖瞭解兩種材料的差異，以及如何在配置賽道記憶體時，如何讓氧化物材料表現的比金屬材料更好。
從在一年多以前開始，Takamura的研究小組試圖打造一款完整的賽道記憶體，因此他們需要SRC製造晶片的協助。如今，UC Davis已經開發出自有的薄膜了，但還必須將晶圓送至橡樹嶺國家實驗室(ORNL)，以便可在凹陷式奈米線中構圖。其他協助Takamura研究小組的組織還包括ORNL奈米相材料科學中心、羅倫斯柏克萊國家實驗室(LBNL)的先進光源中心。
Takamura表示：「我們不會在此時開發賽道記憶體原型。我們目前已經有一項展示可看到賽道記憶體元件採用一種完全不同的材料時應該會發生的類似現像，它和典型採用的金屬材料系統是不一樣的。我們的下一步將會研究奈米線幾何、凹陷的理想形狀，以及我們可封裝的多麼緊密以定義記憶體密度。」
目前仍然存在的挑戰包括為所形成的磁疇壁形狀實現最佳化、控制在奈米線中的位置，以及掌握其沿奈米線賽道的運動。尚待進行最佳化的參數包括施加的磁場與電場密度、光線照射程度、壓力與溫度。
SRC and UC Davis Researchers Explore New Materials and Device Structures to Develop Next-Generation “Race Track Memory” Technologies
RESEARCH TRIANGLE PARK, N.C. (Aug. 12, 2014) – University of California, Davis researchers sponsored by Semiconductor Research Corporation (SRC), the world’s leading university-research consortium for semiconductors and related technologies, are exploring new materials and device structures to develop next-generation memory technologies.
The research promises to help data storage companies advance their technologies with predicted benefits including increased speed, lower costs, higher capacity, more reliability and improved energy efficiency compared to today’s magnetic hard disk drive and solid state random access memory (RAM) solutions.
Conducted by UC Davis’ Takamura Research Group that has extensive experience in the growth and characterization of complex oxide thin films, heterostructures and nanostructures, the research involves leveraging complex oxides to manipulate magnetic domain walls within the wires of semiconductor memory devices at nanoscale dimensions. This work utilized sophisticated facilities available through the network of Department of Energy-funded national laboratories at the Center for Nanophase Materials Sciences, Oak Ridge National Laboratory and the Advanced Light Source, Lawrence Berkeley National Laboratory.
“We were inspired by the ‘Race Track Memory’ developed at IBM and believe complex oxides have the potential to provide additional degrees of freedom that may enable more efficient and reliable manipulation of magnetic domain walls,” said Yayoi Takamura, Associate Professor, Department of Chemical Engineering and Materials Science, UC Davis.
Existing magnetic hard disk drive and solid state RAM solutions store data either based on the magnetic or electronic state of the storage medium. Hard disk drives provide a lower cost solution for ultra-dense storage, but are relatively slow and suffer reliability issues due to the movement of mechanical parts. Solid state solutions, such as Flash memory for long-term storage and DRAM for short-term storage, offer higher access speeds, but can store fewer bits per unit area and are significantly more costly per bit of data stored.
An alternative technology that may address both of these shortcomings is based on the manipulation of magnetic domain walls, regions that separate two magnetic regions. This technology, originally proposed by IBM researchers and named ‘Race Track Memory’, is where the UC Davis work picked up.
With most previous studies focused on metallic magnetic materials and their alloys due to well-established processing steps and high Curie temperatures, challenges still remain in manipulating parameters such as the type of domain walls formed, their position within the nanowires and their controlled movement along the length of the nanowires.
The UC Davis research investigates the use of complex oxides, such as La0.67Sr0.33MnO3 (LSMO), and heterostructures with other complex oxides as candidate materials. Complex oxides are part of an exciting new class of so-called “multifunctional’ materials that exhibit multiple properties (e.g. electronic, magnetic, etc.) and may thereby enable multiple functions in a single device. For the case of LSMO, it is a half metal, exhibits colossal magnetoresistance (CMR), meaning it can dramatically change electrical resistance in the presence of a magnetic field, and undergoes a simultaneous ferromagnetic-to-paramagnetic and metal-to-insulator transition at its Curie temperature.
In addition, these properties are sensitive to external stimuli, such as applied magnetic/electric fields, light irradiation, pressure and temperature. These attributes may allow researchers to better manipulate the position and movement of the magnetic domain walls along the length of the nanowires.
“While still in the early stages, the innovative research from the UC Davis team is helping the industry gain a better fundamental understanding linking the chemical, structural, magnetic and electronic properties of next-generation memory materials,” said Bob Havemann, Director of Nanomanufacturing Sciences at the SRC.
About SRC
Celebrating more than 30 years of collaborative research for the semiconductor industry, SRC defines industry needs, invests in and manages the research that gives its members a competitive advantage in the dynamic global marketplace. Awarded the National Medal of Technology, America’s highest recognition for contributions to technology, SRC expands the industry knowledge base and attracts premier students to help innovate and transfer semiconductor technology to the commercial industry. For more information, visit https://www.src.org/.
MEDIA CONTACT:
Dan Francisco
Integrity Global for SRC
dan@integrityglobal.biz
916-812-8814
編譯：Susan Hong
(參考原文：Racetrack Memory to Beat Hard Drives & Flash，by R. Colin Johnson)
資料來源:電子工程專輯
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