Process Challenges for 1S-1R Crossbar Memory

Transcription

1 Process Challenges for 1S-1R Crossbar Memory W. Kim, M. Frei and M. Pakala

2 OUTLINE Background Crossbar Memory as Storage Class Memory (SCM) Chalcogenide Materials: PCM, OTS Selector Crossbar patterning status Summary and Outlook

3 Higher density, lower $/bit Performance (lower latency, higher BW) On-chip memory New Memory Inflections Address Memory Gaps PC/Server Memory Hierarchy Memory Attributes Volatile or Working Access Speed Endurance CPU/ Register L1 Cache - SRAM L2, L3 Cache - SRAM MRAM Cache Off Chip Memory - DRAM Gap PCM SCM Non Volatile or Storage Retention (non- volatility) Density Local Storage - FLASH Local Storage- HDD Off line - Tape Offline Storage - TAPE 3 PCRAM is non-volatile and faster than flash

4 Integration Schemes for New Memory Embedded in BEOL Crossbar Memory 3D Strings Others 1T-1R 1S-1R 1S-1R, 1T 1T Memor Memory y Selector + memory Thermal budget (FEOL integration) 1T-1C Bottom Electrode Contact, 400 C BEOL thermal budget, Etching & LT Encapsulation 4 Damage free etching at < 60nm pitch ALD of complex compounds/alloys Low leakage HAR FE capacitor formation New materials and integration schemes have new process & equipment requirements

5 Materials Optimization For Performance PCM (example) Reduce SET time for crystallization Lower RESET/SET energy Increase Memory Window OTS Selector Increase I ON /I OFF ratio Lower I OFF current Increase cycling endurance Reduce amorphous chalcogenide V th drift Improve high temperature stability V th Santa 5 Clara, CA

6 Composition Screening by Multi-Cathode PVD Desired Composition Matrix Multi-cathode PVD Co-sputtering Short Loop etest OTS/PCM Chalcogen atoms Control thermal and electrical properties by additives: A Ge, Si: As: Cross linking Stabilize amorphous state B C Multi-cathode for fast composition screening of multi-elemental chalcogenides 6

7 PCM Composition Optimization Composition study by co-sputtering for different device targets envm SET at < 50ns pulse width achieved SCM T x T x LETI-AMAT JDP 2015, 2017 LETI-AMAT JDP PCM composition optimization to address fast SET required for SCM application

8 OTS Composition Optimization V th distribution across 300mm wafer V th drift / cycling endurance* *limited by external current compliance scheme used for testing OTS composition optimization for low V th drift

9 9 Endura TM PVD System Equipment Challenges for PCM Deposition

10 Crossbar Integration Flow and Process Equipment Celera Precision In-situ Oxide / Poly Producer High Density SiN Low Temp Poly, Oxide High selectivity poly High throughput, lower cycle time Low Temp SiN High Density, Range of Film Stress High productivity Producer system B L H M T E Memor y M E OTS Non-volatile Etch Celera SiN Optimized pulsed RF for profile Damage free process Chamber design for uniformity Applied Materials Internal Data Low Temp dielectric Hermetic, low WER, conformal No damage, good adhesion Applied Materials Internal Data WL BE Low temp gap fill FCVD Low Temp dielectric Void free gapfill 10 1 level schematic Applied Materials Internal Data Low damage processes key focus for integrating chalcogenide materials

11 Summary 1S-1R crossbar architecture and, 3D string architecture with PCM suitable for SCM application Etching and encapsulation of chalcogenide materials, without inducing damage (chemical, plasma and thermal), is key challenge for 1S-1R crossbar scaling Applied Materials focusing on High Volume Manufacturing Equipment that enables 1S-1R crossbar device performance, yield and cost. Multiple tools shipped 11