Copyright © 2010 SpectraPlex – Presentation property of SpectraPlex, no reproduction without permission SpectraPlex High Performance Communications Technologies SpectraPlex Flash Technology MANDAN
Copyright © 2010 SpectraPlex – Presentation property of SpectraPlex, no reproduction without permission SpectraPlex High Performance Communications Technologies SpectraPlex Flash - Codename MANDAN n Applies multilevel flash technology to obtain error detection/correction n Simple encoding and decoding n Less silicon overhead than conventional ECC
Copyright © 2010 SpectraPlex – Presentation property of SpectraPlex, no reproduction without permission SpectraPlex High Performance Communications Technologies Benefits of the MANDAN Technology n An increase of 23% or more in gross return per wafer n Improved field reliability – better quality n Simple implementation n No additional silicon required
Copyright © 2010 SpectraPlex – Presentation property of SpectraPlex, no reproduction without permission SpectraPlex High Performance Communications Technologies Cost of Mandan benefits n Addition of ECC encode and decode circuitry – may only require small modifications if ECC is currently employed in chip designs n Small change in program and sense circuitry n New chip layout
Copyright © 2010 SpectraPlex – Presentation property of SpectraPlex, no reproduction without permission SpectraPlex High Performance Communications Technologies Block Overview Input Data Encode to multilevel form Store in flash cells Read multilevel data Decode from multilevel form and apply error detection/correction Output Data
Copyright © 2010 SpectraPlex – Presentation property of SpectraPlex, no reproduction without permission SpectraPlex High Performance Communications Technologies ESC Design Changes Peripheral interface circuitry requires limited modification Memory array remains unchanged or may be reduced in size
Copyright © 2010 SpectraPlex – Presentation property of SpectraPlex, no reproduction without permission SpectraPlex High Performance Communications Technologies Mandan Outline n Proprietary new technology n Implemented with current technologies n Cell arrays in current designs can often be used without modification n Provides Error Correction Coding (ECC) uniquely suited to flash memory systems
Copyright © 2010 SpectraPlex – Presentation property of SpectraPlex, no reproduction without permission SpectraPlex High Performance Communications Technologies Larger memories need lower error rates 1 Mb memory 1 Gb memory Constant number of errors per die Error rate improvement required An error rate of 1e-11 is needed with the larger chip to give the same total number of errors per die
Copyright © 2010 SpectraPlex – Presentation property of SpectraPlex, no reproduction without permission SpectraPlex High Performance Communications Technologies Implications n Error performance sufficient for todays memories will be inadequate for tomorrows n Error mechanisms must be understood and treated n Error detection and correction is essential for next generation and beyond products
Copyright © 2010 SpectraPlex – Presentation property of SpectraPlex, no reproduction without permission SpectraPlex High Performance Communications Technologies Flash Error Mechanisms n Hard Failures –Stuck bit lines –Driver/sense amp failures –Other hard errors n Statistical errors n Soft Failures –Cosmic rays –Transients –Other soft failures
Copyright © 2010 SpectraPlex – Presentation property of SpectraPlex, no reproduction without permission SpectraPlex High Performance Communications Technologies Hard Failure Remedies n Add redundant rows and columns –Adds significant array area –Requires test and fix at production time n Add redundancy and ECC circuitry –Adds some to array area –Adds encode and decode complexity n Use SpectraPlex Mandan ECC –Adds encode and decode complexity –No additional array area needed
Copyright © 2010 SpectraPlex – Presentation property of SpectraPlex, no reproduction without permission SpectraPlex High Performance Communications Technologies Statistical Errors n Result from large distribution around programmed state value n Controlled by programming algorithm n State width roughly inversely proportional to number of states n Trade off time and programming algorithm complexity for state width and better error performance
Copyright © 2010 SpectraPlex – Presentation property of SpectraPlex, no reproduction without permission SpectraPlex High Performance Communications Technologies Soft Failures n Result from usually unpredictable events in normal operation –Cosmic rays and other radiations change cell state –Noise and transients interfere with storage and readback processes n Must be fixed by error correction methods –Conventional ECC requires 8 – 20% more cells and circuit complexity –SpectraPlex ESC only adds to circuit complexity
Copyright © 2010 SpectraPlex – Presentation property of SpectraPlex, no reproduction without permission SpectraPlex High Performance Communications Technologies Optimization n Memory must be optimized for type of errors expected n Hard and soft errors can be handled by similar mechanisms n Statistical errors generally best dealt with through optimization of programming process and ECC
Copyright © 2010 SpectraPlex – Presentation property of SpectraPlex, no reproduction without permission SpectraPlex High Performance Communications Technologies Definition of Terms Min Threshold Voltage Level Max Distribution of cells around nominal level for the particular programmed value 2*Delta Sigma
Copyright © 2010 SpectraPlex – Presentation property of SpectraPlex, no reproduction without permission SpectraPlex High Performance Communications Technologies Relationship between number of states and statistical error rate n Increased number of states reduces distance between states (delta) n Tighter programming required by increase in number of states also reduces width of distribution (sigma) n Result is that ratio of delta/sigma is nearly constant over wide range of number of states n Delta/sigma ratio is most important factor in statistical error rate basic statistical error rate will be roughly constant **IF** sigma can be reduced proportional to delta
Copyright © 2010 SpectraPlex – Presentation property of SpectraPlex, no reproduction without permission SpectraPlex High Performance Communications Technologies SpectraPlex MANDAN and Conventional Performance Compared n Conventional is two bits per cell without error correction n Mandan has better error rate at same delta/sigma ratio and bit density as practical conventional designs n Only one design example shown – actual performance depends on particular design requirements of a specific product SpectraPlex MANDAN performance Conventional 2 bit per cell performance Error RateError Rate delta / sigma ratio Typical range
Copyright © 2010 SpectraPlex – Presentation property of SpectraPlex, no reproduction without permission SpectraPlex High Performance Communications Technologies What do the curves mean? n For the same delta/sigma ratio, Mandan processing can add significant improvement in error rate n For the same error rate, Mandan can reduce requirements on delta/sigma ratio n Designers have more options available to achieve design objectives
Copyright © 2010 SpectraPlex – Presentation property of SpectraPlex, no reproduction without permission SpectraPlex High Performance Communications Technologies Mandan tradeoffs n Mandan can be used to improve basic statistical error rate n Mandan can be used to ease programming requirements = faster programming/write time n Mandan can be used to offset effects of other desirable objectives such as reduced voltage operation
Copyright © 2010 SpectraPlex – Presentation property of SpectraPlex, no reproduction without permission SpectraPlex High Performance Communications Technologies Potential costs of conventional ECC n Increase in number of cells to hold parity check bits –Typically in the range of 8-20% more cells –Depends on block size n Must add encode and decode circuitry –Encode has modest cost –Decode affects access time for reading n Significant intellectual property barriers
Copyright © 2010 SpectraPlex – Presentation property of SpectraPlex, no reproduction without permission SpectraPlex High Performance Communications Technologies Mandan Advantages n Does not require additional cells n Provides error detection/correction n Novel technology – patent pending n Useful across a broad range of densities and operating conditions n Access overhead comparable to conventional ECC
Copyright © 2010 SpectraPlex – Presentation property of SpectraPlex, no reproduction without permission SpectraPlex High Performance Communications Technologies Production Benefits Comparison Example ComparisonConventionalMANDAN wafer size300mm technology92nm capacity4Gb die fraction for error encode/decode3% die fraction for parity check (ECC)10%0% Total die fraction for ECC13%3% Error rate10^-10< 10 ^ -20 good die per wafer cost of processed wafer$800 cost per die$0.465$0.419 savings per die $0.047 value of die at asp of $5.00$8,594$9,550 net per wafer$7,794$8,750 net per 100K wafers$779,375,000$875,000,000 Benefit from SpectraPlex MANDAN $95,625,000 percent benefit 12.3% cost of license (5% of asp) $47,750,000 net benefit after license $47,875,000
Copyright © 2010 SpectraPlex – Presentation property of SpectraPlex, no reproduction without permission SpectraPlex High Performance Communications Technologies For more informations