轉自：https://www.st.com/content/st_com/zh/about/innovation---technology/PCM.html
(嵌入式內存技術正處於十字路口。在FD-SOI和FinFET高級CMOS技術中，傳統浮柵嵌入式非易失性存儲器（eNVM）的集成在28nm和更小的硅幾何結構上是一個重大的技術挑戰。新的NVM技術基於特殊外來材料的功能特性，采用了與Flash存儲器技術完全不同的物理機制，並為28納米CMOS轉變帶來的工藝集成困難提供了更有效的解決方案。在這些常被稱為“新興存儲器”的新型NVM技術中，最成熟的是相變存儲器（PCM）。
相變記憶的基本機制是由斯坦福·羅伯特·奧夫斯基在20世紀60年代發明的。ST持有原始開發的專利許可證，並在這項突破性工作的基礎上發展了15年多，開發了嵌入式PCM解決方案（ePCM），該解決方案如今已集成到我們的28nm FD-SOI技術平台中。
相變存儲器是用鍺銻碲（GST）合金制成的，它利用了材料在非晶態和晶態之間物理性質的快速熱控變化。對應於邏輯0和1的這些狀態通過非晶態（邏輯0）中的高電阻和晶態（邏輯1）中的低電阻進行電區分。PCM在低電壓下讀寫，與Flash和其他嵌入式存儲器技術相比，它具有許多顯著的優勢。)
Embedded Memory technologies are at a crossroads. The integration of conventional floating gate embedded Non-Volatile Memories (eNVM) represents a significant technical challenge at 28nm and smaller silicon geometries in both FD-SOI and FinFET advanced CMOS technologies. New NVM technologies, based on the functional properties of particular exotic materials, employ radically different physical mechanisms than those used with Flash memory technologies and provide a more effective solution to the process integration difficulties raised by the disruptive 28nm CMOS transition. Among these new NVM technologies, often called “emerging memories,” the most mature is Phase-Change Memory (PCM).
The fundamental mechanism for Phase-Change Memory was invented in the 1960s by Stanford Robert Ovshinsky. ST holds a license to the patents that resulted from that original development and has built onto that ground-breaking work for more than 15 years, developing the embedded PCM solution (ePCM) that is today integrated into our 28nm FD-SOI technology platform.
Phase-Change Memory is made using a Germanium Antimony Tellurium (GST) alloy, and takes advantage of rapid heat-controlled changes in the material’s physical property between amorphous and crystalline states. These states, which correspond to logic 0 and 1, are electrically differentiated by high resistance in the amorphous state (logic 0) and low resistance in the crystalline state (Logic 1). PCM, which reads and writes at low voltage, offers several substantial advantages over Flash and other embedded memory technologies.
Phase-Change Memory Technology Architecture
Phase-Change Memory (PCM) array
A cross section of the embedded-PCM bitcell integrated in the 28nm FD-SOI technology shows the heater that quickly flips storage cells between crystalline and amorphous states.
Phase-Change Memory Advantages
Write Performance / Data Retention
With single-bit alterability, PCM technology delivers significantly better write and comparable read performance than Flash-based memories that require at least a byte- or sector-erase cycle before reprogramming. This single-bit alterability simplifies software handling of data storage. ST’s implementation benefits from patented technology related to the memory cell and to the GST alloy to support high-temperature data retention, including during solder reflow, so firmware can be uploaded to ePCMs before mounting and soldering.
High Density / Low Power Roadmap
The speed/power characteristics of the ePCM macro-cell and its roadmap at smaller geometries offer a scalable solution for large embedded memories.
Robust Performance
ST’s PCM technology has been developed and tested to operate within the most stringent automotive requirements for robust high-temperature operation, radiation hardening, and data retention. ePCM achieves automotive requirements for AEC-Q100 Grade 0 with an operating temperature up to +165°C.
Flexible Back-end Process
ePCM is a back-end technology which separates the non-volatile memory-cell process module from the complex logic-transistor modules built in the Front-End. As a Back-End, metallization-based process, ePCM is technology-independent, so it can be embedded in virtually any technology node.
FD-SOI and PCM Combined
Fully Depleted Silicon On Insulator, or FD-SOI, another technology that ST pioneered, is a planar process technology that delivers the benefits of reduced silicon geometries while actually simplifying manufacturing. Combining 28nm FD-SOI and PCM enables memory array sizes that are 4-5 times larger than what Flash on bulk 40nm CMOS can achieve.
Phase-Change Memory Applications
Ever more demanding applications are pushing the limits of MCU architectures due to their need for more processing power, lower power consumption, and larger memory sizes. One of the most challenging demands is for larger embedded memories to hold bigger and more complex firmware.
ePCM presents a solution to these chip- and system-level challenges, while meeting automotive requirements for AEC-Q100 Grade 0, operating at temperature up to +165°C. In addition, ST’s technology assures firmware/data retention through high-temperature soldering reflow processes and immunity to radiation, for additional data safety.
ST presented an update on the architecture and performance of a 16Mb ePCM array for a 28nm FD-SOI automotive MCU at the 2018 International Electron Devices Meeting (IEDM) in San Francisco on December 4, 2018.
Truly Innovative 28nm FDSOI Technology for Automotive Microcontroller Applications embedding 16MB Phase Change Memory：https://www.st.com/content/ccc/fragment/multimedia/e-presentation/technology_pres/group0/63/51/83/98/d4/11/40/7b/IEDM_conference_Dec2018_ARNAUD/files/IEDM_conference_Dec2018_ARNAUD.pdf/jcr:content/translations/en.IEDM_conference_Dec2018_ARNAUD.pdf