How to Identify and Prevent ESD Issues Using PathFinder™ Design Automation Conference 2014 6/23/2014 © 2014 ANSYS, Inc. 1 What is ESD? Electrostatic Discharge “A transfer of charge between two bodies at different electrostatic potentials, either through contact or via an ionized ambient discharge (a spark).” I/O pin Intended path Unintended path ESD Clamps Drain/Source junction or gate-oxide damage I/O buffers ESD Clamps IO Pad High current event causing latent or catastrophic failures to IC Metal/via melt-down 6/23/2014 © 2014 ANSYS, Inc. 2 What is ESD? Human Body/Machine Model(HBM/MM) Charged Device Model(CDM) +++ Discharge currents for different types of ESD events Source: http://www.esda.org/documents/IndustryCouncilWhitePaper2.pdf 6/23/2014 © 2014 ANSYS, Inc. 3 PathFinder™: SoC and IP ESD Integrity Layout (DEF/GDS) Spice Netlist/ Clamp Models Technology gndA vdd vddA PathFinder gnd ESD rules gndB 6/23/2014 © 2014 ANSYS, Inc. vddB 4 PathFinder™: SoC and IP ESD Integrity Layout (DEF/GDS) Spice Netlist/ Clamp Models Technology ESD rules R-Extraction gndA vddA PathFinder gnd vdd gndB 6/23/2014 © 2014 ANSYS, Inc. vddB 5 PathFinder™: SoC and IP ESD Integrity Layout (DEF/GDS) Spice Netlist/ Clamp Models Technology Layout Connectivity Checks Layout Connectivity Checks gndA X vddA PathFinder gnd vdd Disconnected clamps Missing pin2pin ESD path Isolated bumps gndB 6/23/2014 ESD rules © 2014 ANSYS, Inc. vddB 6 PathFinder™: SoC and IP ESD Integrity Layout (DEF/GDS) Layout Connectivity Checks gnd vdd gndA R? vddA R? R? Any Point R? R? gndB 6/23/2014 ESD rules Resistance Checks PathFinder Resistance Checks Spice Netlist/ Clamp Models Technology © 2014 ANSYS, Inc. R? vddB 7 PathFinder™: SoC and IP ESD Integrity Layout (DEF/GDS) Layout Connectivity Checks gnd gndA X vddA Interconnect Failure Checks vdd R? Metal/via bottlenecks Disconnected Any R? clamps Point Missing pin2pin ESD path R? R? R? R? Isolated Current crowding bumps on diode fingers gndB 6/23/2014 ESD rules Interconnect Failure Checks Layout Connectivity Checks Resistance Checks R-Extraction PathFinder Resistance Checks Spice Netlist/ Clamp Models Technology © 2014 ANSYS, Inc. vddB 8 PathFinder™: SoC and IP ESD Integrity Layout (DEF/GDS) Layout Connectivity Checks Dynamic Checks gnd gndA X vddA Interconnect Failure Checks vdd R? Root-cause Analysis Metal/via bottlenecks Disconnected Any R? clamps Point IP/Full-chip Capacity Missing pin2pin ESD path Monitor device stress R? R? R? R? Early Stage to Sign-off Isolated Current crowding bumps on diode fingers gndB 6/23/2014 ESD rules Dynamic Checks Interconnect Failure Checks Layout Connectivity Checks Resistance Checks R-Extraction PathFinder Resistance Checks Spice Netlist/ Clamp Models Technology © 2014 ANSYS, Inc. vddB 9 Common ESD Issues in SoCs ESD Failure Types ESD Device 40% BEOL 30% misc 5% ESD Cross Network Domain 10% 15% Device breakdown Interconnect melt-down Cross-domain ESD issues ESD failures impact first silicon success 6/23/2014 © 2014 ANSYS, Inc. 10 Device Breakdown Why is it more important now? What are the common causes for such failures? ESD Design window from 130 nm to 32 nm technology High ESD bus resistance +ve Zap Power2 Ground Zap vcc V>V(break-down) D1 sig D2 Source: Cao et al., ESD design challenges and strategies in deeplyscaled integrated circuits, PhD dissertation, Stanford Univ, 2010. 6/23/2014 -ve Zap vss © 2014 ANSYS, Inc. Functional devices Inefficient or missing clamps 11 Device Breakdown # Signal bus R check BEGIN_ESD_RULE NAME sigbump2diode_Rcheck TYPE BUMP2CLAMP ARC_R 0.1 TERMINAL_NET_GROUP SIGNAL CLAMP_TYPE1 D1 D2 END_ESD_RULE How can PathFinder help ? Power Bus Resistance check Signal Bus R checks #Power Bus R Check BEGIN_ESD_RULE NAME Pwr_Bus_R_check TYPE CLAMP2CLAMP ARC_R 0.1 TERMINAL_NET_GROUP POWER GROUND FROM_CLAMP_TYPE D1 D2 TO_CLAMP_TYPE PWRCLMP END_ESD_RULE #Power2Ground R check BEGIN_ESD_RULE NAME PWR2GND_R_check TYPE BUMP2BUMP LOOP_R 5 PARALLEL_R 1 TERMINAL_NET_GROUP POWER GROUND CLAMP_TYPE PWRCLMP SHORT_BUMP_IN_NET_GROUP POWER GROUND END_ESD_RULE 6/23/2014 vcc D1 Functional devices sig D2 vss Power2Ground R check © 2014 ANSYS, Inc. 12 Interconnect Melt-down Why is it more important now? What are the common causes for such failures? Current crowding on ESD device Insufficient via-cuts/ ineffective clamps Positive Zap VCC IO Pad D1 Clamps Pad D2 Negative Zap Mx My Mz RD L 6/23/2014 VSS Insufficient wire width on ESD pathways © 2014 ANSYS, Inc. 13 Interconnect Melt-down How can PathFinder help ? # Signal bus CD check BEGIN_ESD_RULE NAME signal_bump2diode_CD_check TYPE CD ZAP_CURRENT 1.3A # ~2kV HBM zap B2C_NET_GROUP SIGNAL SHOTGUN_MODE 1 END_ESD_RULE #Power Bus CD Check BEGIN_ESD_RULE NAME Pwr_Bus_CD_check TYPE CD ZAP_CURRENT 1.3A #~2kV HBM Zap C2C_NET_GROUP POWER GROUND FROM_CLAMP_TYPE D1 D2 TO_CLAMP_TYPE PWRCLMP END_ESD_RULE #Power2Ground CD check BEGIN_ESD_RULE NAME PWR2GND_CD_check TYPE BUMP2BUMP ZAP_CURRENT 1.3A # ~2kV HBM Zap TERMINAL_NET_GROUP POWER GROUND CLAMP_TYPE PWRCLMP SHORT_BUMP_IN_NET_GROUP POWER GROUND END_ESD_RULE 6/23/2014 Power2Ground CD checks Signal Bus CD checks Power/Ground Bus CD checks VCC IO Pad Power Clamps D1 Pad D2 Define Interconnect CD limits Mx = x mA/um My = y mA/um Mz = z mA/um RDL = r mA/um © 2014 ANSYS, Inc. # Clamp IV Model BEGIN_CLAMP_IV NAME <I-V_clamp_name> Ron <Ron+> [<Ron->] VT1 <VT1+> [<VT1->] VH <VH+> [<VH->] ROFF <Roff+> [<Roff->] END_CLAMP_IV VSS 14 Cross-domain ESD Issues Why is it more important now? CPU CORE (VDDC) High Speed I/O GPU (VDDG) VDD2 VDD1 Power Clamp VSS1 Analog/RF (AVDD) Memory/Cache (VDDM) Unintentional ESD discharge path Intentional ESD discharge path RVSS GPIO Analog IO GPIO GPIO What are the common causes for such failures? GPIO Bridge diodes High Ground bus R Power Clamp VSS2 Insufficient/unconnected bridge diodes Bridge diodes 6/23/2014 © 2014 ANSYS, Inc. 15 Cross-domain ESD Issues How can PathFinder help ? # Clamp connectivity Checks in PathFinder TCL> perform clampcheck # pin2pin connectivity \ –allNetConn # report disconnected net pairs \ -rptDisconn # Signal bus CD check BEGIN_ESD_RULE NAME VSS_bus_R_Check TYPE C2C FROM_CLAMP_TYPE PWRCLMP TO_CLAMP_TYPE B2B_DIODE ARC_R 0.5 END_ESD_RULE #Cross-domain CD Check BEGIN_ESD_RULE NAME Cross_domain_CD_Check TYPE CD ZAP_CURRENT 1.3A #~2kV HBM Zap NET_PAIR VDD1 VSS2 END_ESD_RULE 6/23/2014 Cross-domain CD checks VDD1 VDD2 Power Clamp VSS1 Power Clamp VSS2 RVSS Bus Resistance Checks Bridge diodes Bridge diodes © 2014 ANSYS, Inc. Clamp connectivity checks 16 PathFinder Core Technologies & Benefits Capacity Accuracy Usability IV curve support Current crowding on diode fingers Root-cause the bottleneck in ESD bus Full-chip capacity with package impact 6/23/2014 ESD snap-back device modeling © 2014 ANSYS, Inc. Rich GUI for debug and optimization 17 ESD-aware SoC Design Flow Analysis driven clamp placement gnd ESD Clamp 6/23/2014 IO Ring IP level Floor plan © 2014 ANSYS, Inc. X GPU (VDDG) Analog/ RF (AVDD) CPU CORE (VDDC) Memory/Cache (VDDM) GPIO ESD Clamp ESD Clamp High Speed I/O GPIO GPIO vdd IO Pad level Resistance and current density limit sign-off Analog IO IO ring ESD bus planning GPIO Final sign-off 18 Summary • Full chip-level ESD integrity analysis solution • PathFinder coverage: – Layout connectivity checks – Resistance checks – Interconnect failure checks – Dynamic CDM checks for IPs • 6/23/2014 Part of ESDA reference flow and TSMC reference flow © 2014 ANSYS, Inc. 19
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