Conference paper ESD Design Challenges in nano-cmos SoC Design SoC conference 2008 The Silicon Controlled Rectifier ( SCR ) is widely used for ESD protection due to its superior performance and clamping capabilities. However, many believe that SCR based ESD protection is prone to latch up, competitive triggering, long development cycles and slow trigger speed. This paper provides an overview of the problems and corresponding design solutions available.
SARNOFF EUROPE ESD DESIGN SOLUTIONS ESD Design Challenges in nano-cmos SoCDesign November 2008 Benjamin Van Camp Savant Company Inc. The 6th International System-on-Chip (SoC) Conference, Exhibit, and Workshops November 2008, Newport Beach, California Sarnoff Europe ESD design solutions On-chip ESD solutions Enable customers to integrate product proven ESD solutions in their ICs Faster time to market Lower R&D/IP risk and expense Track record in 8 CMOS generations, BiCMOSand BCD Since 2007: 32 ICs released in 65nm CMOS July 2008: 40nm ESD solutions validated in silicon! IDM, Fabless customers and foundry partners TSMC DCA partner, UMC IP Alliance partner Toshiba, SONY, Infineon, Altera, PMC, Gennum, Actel, THine, AMIS, RedMere, ON 75 137 222 354 450 '04 '05 '06 '07 '08 Proprietary & Confidential 2 1
Purpose of this presentation Highlight ESD threats in advanced SoC s in 45 and beyond IO and core protection is not enough Case studies: Core failures during ESD testing found Provide clarification Failures at interfaces between functional blocks Overview of dangerous situations Propose solutions Silicon and product proven approach Proprietary & Confidential 3 Outline Introduction ESD issues in System on Chip (SoC) Conclusions Proprietary & Confidential 4 2
What is Electro Static Discharge (ESD)? What is Electrostatic Discharge ( ESD )? The sudden discharge of a charged body Short time (<1us) Short rise time (<10ns) High current levels (1-10A) ESD damages in integrated circuits Industry quotes about ESD failures: Responsible for 20-30% of IC failures 25.8% of the products rejected Estimated 8 to 33% of all product losses Proprietary & Confidential 5 How to deal with ESD? ESD protection approach Solution: On-chip ESD protection clamps Included in IO library ESD tolerant driver design (foundry guidelines) Does this solve all stress cases? V DD IN Core OUT Proprietary & Confidential 6 3
Outline Introduction ESD issues in System on Chip (SoC) SoC complexity ESD in advanced CMOS Investigation of most dangerous cases Conclusions Proprietary & Confidential 7 System on Chip complexity background System on Chip (SoC) Advanced technology nodes: 65nm, 45nm Multi million $ investment Mask costs Innovation Design Tools High revenue based products to justify the substantial cost of investment Complex architecture Multiple voltage domains Multiple IP blocks from various vendors ESD difficulty increasing... Due to advanced technology and product complexity Proprietary & Confidential 8 4
ESD Design Margin evaporates for advanced CMOS Decreasing solution space Normal operation (VDD) Slight decrease Node [nm] 500 Vdd Technology scaling 350 250 180 130 90 65 45 0 5 10 15 20 V 25 [V] Proprietary & Confidential 9 ESD Design Margin evaporates for advanced CMOS Decreasing solution space Normal operation (VDD) Slight decrease Maximum voltage decreases rapidly Transient breakdown of gate oxides Burn-out of output drivers Core failure voltage Node [nm] 500 350 250 180 130 90 65 45 Vdd Maximum voltage 0 5 10 15 20 V 25 [V] Proprietary & Confidential 10 5
ESD Design Margin evaporates for advanced CMOS Decreasing solution space Normal operation (VDD) Slight decrease Maximum voltage decreases rapidly Transient breakdown of gate oxides Burn-out of output drivers Core failure voltage Difference = ESD design window Rapid reduction of design margins Node [nm] 500 350 250 180 130 90 65 45 Vdd ESD design window Maximum voltage 0 5 10 15 20 V 25 [V] 45nm/40nm: ESD design space reduced to 3V! Proprietary & Confidential 11 Outline Introduction ESD issues in System on Chip (SoC) SoC complexity ESD in advanced CMOS Investigation of most dangerous cases Conclusions Proprietary & Confidential 12 6
How about your ASIC circuits? Dangerous situations (1/4) Cause: Include on-chip decoupling capacitors Stabilize Vdd supply potential Reduce board level components: BOM Designers use GOX1 gate capacitance: highest Cap/area Problem: LV Core breakdown determined by sensitive thin gate oxide Reduced ESD design margin Solution: Low voltage triggered power clamp GOX1 capacitance V dd V ss Core block Proprietary & Confidential 13 How about your ASIC circuits? Dangerous situations (2/4) Cause: Analog tricks to improve circuit speed Include core transistors in 3.3V domain Designers use GOX1 transistor for speed reasons Designers do not use ESD foundry rules 3.3V V DD Problem: HV Core breakdown determined by sensitive thin gate transistor Reduced ESD design margin D+ LV transistors Solution: Low voltage triggered power clamp for High Voltage domain HV transistor Proprietary & Confidential 14 7
How about your ASIC circuits? Dangerous situations (3/4) Cause: Cascode configurations Increase signal voltage tolerance (5V tolerant) Designers do not use ESD foundry rules Problem: Unballasted cascode design ESD sensitive Reduced ESD design margin Up to 5V 3.3V V DD Solution: Improved cascode layout Local (IO) protection approach Proprietary & Confidential 15 How about your ASIC circuits? Issues 1-3 Reduced ESD design margins Example solution 40nm CMOS 0.9V domain 3.6kV HBM 245V MM < 100pA leakage I [A] 2 1.5 40nm 0.9V power clamp example 33 um 1 0.5 Vh > Vdd + 10% Vt1 > Vdd + 50% 38 um 0 0 1 2 3 4 5 V [V] 6 Proprietary & Confidential 16 8
SoC s add another level of complexity SoC s main ESD problem? IP block 1: Within specs Fully qualified for ESD protection Silicon proven, product proven IP#1 alone >2kV HBM, >500V CDM 1.2V V DD IP #1 Proprietary & Confidential 17 SoC s add another level of complexity SoC s main ESD problem? IP block 1: Within specs Fully qualified for ESD protection Silicon proven, product proven IP block 2: Above specs Fully qualified for ESD protection Silicon proven, product proven IP#1 alone >2kV HBM, >500V CDM 1.2V V DD IP#2 alone >4kV HBM, >1000V CDM 1.2V V DD IP #1 IP #2 Proprietary & Confidential 18 9
SoC s add another level of complexity SoC s main ESD problem? IP block 1: Within specs Fully qualified for ESD protection Silicon proven, product proven IP block 2: Above specs Fully qualified for ESD protection Silicon proven, product proven IP#1 alone >2kV HBM, >500V CDM 1.2V V DD Full product <1kV HBM, <100V CDM IP#2 alone >4kV HBM, >1000V CDM 1.2V V DD Wired together in SoC: Below spec Functionality: OK ESD qualification: below spec! Which IP provider is responsible? IP #1 IP #2 Proprietary & Confidential 19 How about your ASIC circuits? Dangerous situations (4/4) Cause: Multiple functional core blocks separately biased Multiple voltage domains (Digital, Analog, IO,...) Multiple IP blocks from various vendors Problem: Unprotected internal / on-chip communication lines 1.2V V DD 1.2V V DD Solution: Ground to ground Improved cascode layout Local (IO) protection approach 1.2V 1.2V Proprietary & Confidential 20 10
Industry reports on this issue since 90nm node Worley (Conexant), 2004 Oxide failure at receiving circuit Signal line between 2 domains Different solution approaches Remote blocks Adjacent blocks Hayashi (Oki), 2004 ESD failure at signal line between two supply units Reason: slow power/core protection (SB NMOS) Brennan (IBM), 2004 Proprietary & Confidential slide 21 Outline Introduction ESD issues in System on Chip (SoC) Conclusions Proprietary & Confidential 22 11
Conclusions Growing difficulty for ESD protection Advanced CMOS Complex System-on-Chip designs Public solutions Exploding silicon cost, increased risk (Industry group) IO based protection not suffucient Core interface circuits need specific care Solutions available Treat on-chip interfaces as external interfaces for ESD Include protection clamps at sensitive receiver Proprietary & Confidential 23 Simple solution to core failures? L. Avery (Sarnoff patent), 1996 Rubber band technique Multi domain core protection Isolation resistance to limit the current Local gate protection for most sensitive gates VDD1 VDD2 GND1 GND2 Proprietary & Confidential slide 24 12
Contact us TakeCharge Technology Benjamin Van Camp Bart Keppens bvancamp@sarnoffeurope.com bkeppens@sarnoffeurope.com TakeCharge Business Katty Van Mele Koen Verhaege kvanmele@sarnoffeurope.com kverhaege@sarnoffeurope.com Sarnoff Europe Brugsebaan 188A, B-8470 Gistel, BELGIUM (tel) +32-59-275-915, (fax) +32-59-275-916 www.sarnoffeurope.com Proprietary & Confidential 25 13
About Sofics Sofics (www.sofics.com) is the world leader in on chip ESD protection. Its patented technology is proven in more than a thousand IC designs across all major foundries and process nodes. IC companies of all sizes rely on Sofics for offthe shelf or custom crafted solutions to protect overvoltage I/Os, other nonstandard I/Os, and high voltage ICs, including those that require system level protection on the chip. Sofics technology produces smaller I/Os than any generic ESD configuration. It also permits twice the IC performance in high frequency and high speed applications. Sofics ESD solutions and service begin where the foundry design manual ends. ESD SOLUTIONS AT YOUR FINGERTIPS Our service and support Our business models include Single use, multi use or royalty bearing license for ESD clamps Services to customize ESD protection o Enable unique requirements for Latch up, ESD, EOS o Layout, metallization and aspect ratio customization o Area, capacitance, leakage optimization Transfer of individual clamps to another target technology Develop custom ESD clamps for foundry or proprietary process Debugging and correcting an existing IC or IO ESD testing and analysis Notes As is the case with many published ESD design solutions, the techniques and protection solutions described in this data sheet are protected by patents and patents pending and cannot be copied freely. PowerQubic, TakeCharge, and Sofics are trademarks of Sofics BVBA. Version May 2011 Sofics BVBA Groendreef 31 B 9880 Aalter, Belgium (tel) +32 9 21 68 333 (fax) +32 9 37 46 846 bd@sofics.com RPR 0472.687.037 Sofics Proprietary 2011