Paul C. Parries

Embedded DRAM: technology platform for the Blue Gene/L chip

The Blue Gene®/L chip is a technological tour de force that embodies the system-on-a-chip concept in its entirety. This paper outlines the salient features of this 130-nm complementary metal oxide semiconductor (CMOS) technology, including the IBM unique embedded dynamic random access memory (DRAM) technology. Crucial to the execution of Blue Gene/L is the simultaneous instantiation of multiple PowerPC® cores, high-performance static random access memory (SRAM), DRAM, and several other logic design blocks on a single-platform technology. The IBM embedded DRAM platform allows this seamless integration without compromising performance, reliability, or yield. We discuss the process architecture, the key parameters of the logic components used in the processor cores and other logic design blocks, the SRAM features used in the L2 cache, and the embedded DRAM that forms the L3 cache. We also discuss the evolution of embedded DRAM technology into a higher-performance space in the 90-nm and 65-nm nodes and the potential for dynamic memory to improve overall memory subsystem performance.

22nm High-performance SOI technology featuring dual-embedded stressors, Epi-Plate High-K deep-trench embedded DRAM and self-aligned Via 15LM BEOL

We present a fully-integrated SOI CMOS 22nm technology for a diverse array of high-performance applications including server microprocessors, memory controllers and ASICs. A pre-doped substrate enables scaling of this third generation of SOI deep-trench-based embedded DRAM for a dense high-performance memory hierarchy. Dual-Embedded stressor technology including SiGe and Si:C for improved carrier mobility in both PMOS and NMOS FETs is presented for the first time. A hierarchical BEOL with 15 levels of copper interconnect including self-aligned via processing delivers high performance with exceptional reliability.

An 800-MHz embedded DRAM with a concurrent refresh mode

An 800-MHz embedded DRAM macro employs a memory cell utilizing a device from the 90-nm high-performance technology menu; a 2.2-nm gate oxide 1.5 V IO device. A concurrent refresh mode is designed to improve the memory utilization to over 99% for a 64 /spl mu/s data retention time. A concurrent refresh scheduler utilizes up-count and down-count registers to identify at least one array to be refreshed at every clock cycle, emulating a classical distributed refresh mode. A command multiplier employs low frequency phased clock signals to generate the clock, commands, and addresses at rates up to 4/spl times/ that of the tester frequency. The macro integrates masked redundancy allocation logic during at speed multibank test. The hardware results show a 312-MHz random access frequency and 800-MHz multibank frequency at 1.2 V, respectively.

A 500MHz Random Cycle 1.5ns-Latency, SOI Embedded DRAM Macro Featuring a 3T Micro Sense Amplifier

A prototype SOI embedded DRAM macro is developed for high-performance microprocessors and introduces performance-enhancing 3T micro sense amplifier architecture (muSA). The macro was characterized via a test chip fabricated in a 65nm SOI deep-trench DRAM process. Measurements confirm 1.5ns random access time with a 1V supply at 85deg and low voltage operation with a 600mV supply.

Scaling deep trench based eDRAM on SOI to 32nm and Beyond

A high performance embedded DRAM with deep trench capacitor and high performance SOI logic has been deployed in 45nm and 32nm technology nodes. Following a yield ramp of the sub-2ns latency 45nm technology, we present, for the first time, a 32nm eDRAM technology fully compatible with high performance logic with high-к metal gate access transistor and high-к node dielectric for the deep trench storage capacitor. We also describe the technology advancements required to scale the deep trench as well as the access transistor for optimal cell retention and performance. A clear scaling path is seen for the 22nm technology node.

A 1 MB Cache Subsystem Prototype With 1.8 ns Embedded DRAMs in 45 nm SOI CMOS

We describe a single voltage supply, 1 MB cache subsystem prototype that integrates 2 GHz embedded DRAM (eDRAM) macros with on-chip word-line voltage supply generation , a 4 Kb one-time-programmable read-only memory (OTPROM) for redundancy and repair control, on-chip OTPROM programming voltage generation, clock generation and distribution, array built-in self-test circuitry (ABIST), user logic and pervasive logic. The eDRAM employs a programmable pipeline, achieving 1.8 ns latency, and features concurrent refresh capability.

Analysis of Retention Time Distribution of Embedded DRAM - A New Method to Characterize Across-Chip Threshold Voltage Variation

In this paper, we investigate the retention time distribution of IBMs 65nm node embedded DRAM. We demonstrate that subthreshold current is the dominant leakage mechanism that determines data retention time, and the retention distribution can be attributed to array Vt variation. Based on this study, we present a new technique for characterization of across-chip Vt variation. The Vt median value and standard deviation of transfer devices within an eDRAM array are estimated by analyzing the retention characteristics. The evaluation results are confirmed by the parametric test data. The proposed method is fast and can be used to monitor Vt variation in both technology development and manufacture. The impact of array Vt spread on the retention and performance of eDRAM is discussed.

45-nm silicon-on-insulator CMOS technology integrating embedded DRAM for high-performance server and ASIC applications

The 45-nm technology, called 12S and developed for IBM POWER7®, is an extremely robust and versatile technology platform that allows for a rich set of features that include embedded dynamic random access memory (DRAM), performance and dense static RAM (SRAM), a trench-based decoupling capacitor, a comprehensive device menu, and a high-performance hierarchical back-end interconnect scheme, all built on a silicon-on-insulator (SOI) substrate. Embedded DRAM was implemented for production in high-performance SOI for the first time and allowed us to leapfrog two generations of conventional SRAM densities. Immersion lithography was also employed for the first time in 45-nm IBM products. Our 45-nm design point represents a judicious leverage of silicon oxynitride dielectrics, scaled device technology, and rich features to yield chip-level performance enhancement of more than 50%, compared with our 65-nm node at comparable or less power. This paper describes the salient features of this technology node, the process architecture, the device design rationale, and the process design interactions.

A novel, low-cost deep trench decoupling capacitor for high-performance, low-power bulk CMOS applications

We present an overview and electrical results for a novel deep trench decoupling capacitor. The process of this decoupling capacitor borrows from the regular embedded DRAM trench process, but with significant process simplification for decoupling use which provide reduced cost and reduced process cycle time. This capacitor can provide significant chip-level area savings, using only 1/8 silicon real estate to fabricate the same capacitance as standard planar gate oxide capacitors. Additionally, the trench decap demonstrates a dramatic improvement in leakage compared to standard planar gate oxide capacitors - as much as 105 improvement in leakage can be realized using trench decaps instead of conventional planar decap designs.

A 0.127 μm 2 High Performance 65nm SOI Based embedded DRAM for on-Processor Applications

The authors present a 65nm embedded DRAM cell (0.127 μm2 cell size) on unpatterned SOI fabricated using standard high performance SOI technology with dual stress liner (DSL). The cell utilizes a low-leakage 2.2-nm gate oxide pass transistor and a deep trench capacitor. A trench side wall spacer process enables a simplified collarless process. Connection to the buried plate is realized by silicided substrate guardrings with fully landed tungsten contacts. The bitline structure and the deep trench capacitor are designed for high transfer ratio and low RC constant which ensure high performance and sufficient sensing signal. The pass transistor is strain engineered to boost on current and employs optimized S/D junctions to help attain sub-pA off current. This technology has produced fully-functional 2Mb prototype embedded macros with sub-1.5ns latency and sub-2ns random cycle times for on-processor caches. The low leakage device developed also enables for the first time a low standby power SOI technology