SpectraPlex Flash Technology

1. SpectraPlex Flash Technology MANDAN

2. SpectraPlex Flash - Codename MANDAN • Applies multilevel flash technology to obtain error detection/correction • Simple encoding and decoding • Less silicon overhead than conventional ECC

3. Benefits of the MANDAN Technology • An increase of 23% or more in gross return per wafer • Improved field reliability – better quality • Simple implementation • No additional silicon required

4. Cost of Mandan benefits • Addition of ECC encode and decode circuitry – may only require small modifications if ECC is currently employed in chip designs • Small change in program and sense circuitry • New chip layout

5. 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

6. ESC Design Changes Peripheral interface circuitry requires limited modification Memory array remains unchanged or may be reduced in size

7. Mandan Outline • Proprietary new technology • Implemented with current technologies • Cell arrays in current designs can often be used without modification • Provides Error Correction Coding (ECC) uniquely suited to flash memory systems

8. Larger memories need lower error rates 1 Gb memory 1 Mb memory Error rate improvement required Constant number of errors per die An error rate of 1e-11 is needed with the larger chip to give the same total number of errors per die

9. Implications • Error performance sufficient for today’s memories will be inadequate for tomorrow’s • Error mechanisms must be understood and treated • Error detection and correction is essential for next generation and beyond products

10. Flash Error Mechanisms • Hard Failures • Stuck bit lines • Driver/sense amp failures • Other hard errors • Statistical errors • Soft Failures • Cosmic rays • Transients • Other soft failures

11. Hard Failure Remedies • Add redundant rows and columns • Adds significant array area • Requires test and fix at production time • Add redundancy and ECC circuitry • Adds some to array area • Adds encode and decode complexity • Use SpectraPlex Mandan ECC • Adds encode and decode complexity • No additional array area needed

12. Statistical Errors • Result from large distribution around programmed state value • Controlled by programming algorithm • State width roughly inversely proportional to number of states • Trade off time and programming algorithm complexity for state width and better error performance

13. Soft Failures • 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 • Must be fixed by error correction methods • Conventional ECC requires 8 – 20% more cells and circuit complexity • SpectraPlex ESC only adds to circuit complexity

14. Optimization • Memory must be optimized for type of errors expected • Hard and soft errors can be handled by similar mechanisms • Statistical errors generally best dealt with through optimization of programming process and ECC

15. Definition of Terms 2*Delta Sigma Distribution of cells around nominal level for the particular programmed value Min Threshold Voltage Level Max

16. Relationship between number of states and statistical error rate • Increased number of states reduces distance between states (delta) • Tighter programming required by increase in number of states also reduces width of distribution (sigma) • Result is that ratio of delta/sigma is nearly constant over wide range of number of states • 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

17. SpectraPlex MANDAN and Conventional Performance Compared • Conventional is two bits per cell without error correction • Mandan has better error rate at same delta/sigma ratio and bit density as practical conventional designs • Only one design example shown – actual performance depends on particular design requirements of a specific product Er ror Rate Conventional 2 bit per cell performance SpectraPlex MANDAN performance delta / sigma ratio Typical range

18. What do the curves mean? • For the same delta/sigma ratio, Mandan processing can add significant improvement in error rate • For the same error rate, Mandan can reduce requirements on delta/sigma ratio • Designers have more options available to achieve design objectives

19. Mandan tradeoffs • Mandan can be used to improve basic statistical error rate • Mandan can be used to ease programming requirements = faster programming/write time • Mandan can be used to offset effects of other desirable objectives such as reduced voltage operation

20. Potential costs of conventional ECC • Increase in number of cells to hold parity check bits • Typically in the range of 8-20% more cells • Depends on block size • Must add encode and decode circuitry • Encode has modest cost • Decode affects access time for reading • Significant intellectual property barriers

21. Mandan Advantages • Does not require additional cells • Provides error detection/correction • Novel technology – patent pending • Useful across a broad range of densities and operating conditions • Access overhead comparable to conventional ECC

22. Production Benefits Comparison

23. For more informations e-mail CTO@SpectraPlex.com