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`October 5th, 2012
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`Version 1.2
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` Ultra MLC Technology Introduction
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`Author: Ethan Chen/ Tones Yen
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`E-mail: ethan.chen@advantech.com.tw; tones.yen@advantech.com.tw
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`www.advantech.com
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`Vervain Ex. 2002, p. 1
`Micron v. Vervain
`IPR2021-01548
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`October 5th, 2012
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`Version 1.2
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`Table of Contents
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`1. Introduction ....................................................................................................... 1
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`2. Flash Memory .................................................................................................... 1
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`a. Physical Structure ................................................................................................................... 1
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`b. Types of NAND Flash ............................................................................................................. 3
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`3. Ultra-MLC .......................................................................................................... 4
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`a. Introduction .............................................................................................................................. 4
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`b. Advantage(s) ........................................................................................................................... 5
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`4. Performance ...................................................................................................... 5
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`Observations ............................................................................................................................... 5
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`5. Endurance ......................................................................................................... 6
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`Testing Methodology .................................................................................................................. 6
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`Observations ............................................................................................................................... 6
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`6. Conclusion(s) ..................................................................................................... 7
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`Appendix A ........................................................................................................... 8
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`www.advantech.com
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`Vervain Ex. 2002, p. 2
`Micron v. Vervain
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`1. Introduction
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`Flash memory
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`is a non-volatile storage element
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`that can be electrically
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`programmed/re-programmed and erased. As technology continuously advances, the
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`demands for greater density and better performance with flash memory become large as well.
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`Most importantly, flash memory is no longer a component that resides only in your
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`computer – It could act as a photo album or a file cabinet that stores all your personal
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`treasures or business portfolios.
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`
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`The purpose of this paper is to provide an overview on flash technology, specifically on NAND
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`flash, a memory technology that has been deeply connected to our day-to-day life. In addition,
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`we would like to introduce another MLC flash member, Ultra MLC, which delivers better
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`performance and endurance – just like the legendary SLC flash.
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`
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`The paper is organized as follows: Section 2 explains the differences between NAND and
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`NOR flash, and provides information on NAND flash including SLC and MLC. Section 3
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`introduces Ultra MLC – the mechanism and its advantages. Section 4 and 5 provide
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`performance and endurance information with Ultra MLC, respectively. Finally, a conclusion is
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`provided.
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`2. Flash Memory
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`Physical Structure
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`NAND and NOR are the types of flash memory, commonly taken side-by-side for comparison
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`due to their nature in data storing. To distinguish their differences, one could think that NOR
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`flash is used for code storage whereas NAND flash is used for file storage.
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`The reason for such a differentiation comes from the fact that NOR flash is capable of
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`achieving fast random access and performing fast read operations, but is restricted by slower
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`write and erase operations. Therefore, NOR flash is more suitable for infrequent data
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`modification, and it is common to see that boot code, firmware or operating system to be
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`stored in NOR flash.
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`1
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`www.advantech.com
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`Vervain Ex. 2002, p. 3
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`On the other hand, NAND flash is capable of performing fast write and erase operations. It
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`also consumes less layout area, which could be translated to greater density and lower
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`cost-per-bit. Almost as good as it sounds, NAND flash has one thing that is unable to
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`outperform NOR flash: That is, slower random access, as the trade off to space saving.
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`Nevertheless, NAND flash is still widely used in various types of file storage elements such as
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`USB flash drives and memory cards, where data constantly needs to be loaded and updated.
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`Figure 1 represents the physical differences between NOR and NAND flash. The NOR
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`structure (Left) is designed to connect each memory cell (highlighted in yellow) vertically,
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`whereas the NAND structure (Right) is designed to connect each memory cell (highlighted in
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`yellow) horizontally. 10F2 and 4F2 represent the layout area per cell for NOR and NAND,
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`respectively. As we mentioned before, NAND flash requires less layout-area consumption
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`and therefore delivers a wider range of capacities and lower bit-cost.
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`Figure 1: (Left) Cell Array for NOR and (Right) Cell Array for NAND
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`2
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`In the rest of the paper, we will focus on NAND flash and introduce Phison’s unique design of
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`Ultra MLC including its mechanism, performance and endurance.
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`www.advantech.com
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`Vervain Ex. 2002, p. 4
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`Types of NAND Flash
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`Generally, NAND flash is categorized in two types – SLC (single-level cell) and MLC
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`(multi-level cell). NAND-makers have recently announced the latest flash technology - TLC
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`(ternary-level cell), also known as three-bit per cell, which is the new addition to the NAND
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`family. However, it is beyond the scope of our topic, and will not be covered in the paper.
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`3
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`Figure 2: Basic Structure of a Memory Cell
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`Each cell is consisted of a single transistor and a floating gate, which is located between Gate
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`and Source/Drain and allows electrons to be stored inside, as shown in Figure 2. For SLC
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`flash, only one bit could be stored to each cell at a time, and there will be two possible states
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`for each cell – 0 or 1. As for MLC flash, two bits could be stored to each cell at a time and
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`there will be four possible states for each cell – 00, 01, 10 or 11. Cell state is determined by
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`the threshold voltage (Vt) of each cell, and the voltage is an interpretation of the amount of
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`charges stored inside the floating gate, as shown in Figure 3.
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`Figure 3: Cell Distribution vs. Threshold Voltage for SLC Flash (Left) and MLC Flash
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`(Right), Respectively
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`Because MLC flash stores 1 more bit at each cell than SLC flash does, MLC provides higher
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`density and lower bit-cost. Unfortunately, nothing comes for free – the trade off for cost-saving
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`is greater power consumption and poorer endurance, due to more voltage levels required and
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`technology limitation. It is common to see that SLC flash is used in industrial applications,
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`whereas MLC flash is used in commercial applications.
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`www.advantech.com
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`Vervain Ex. 2002, p. 5
`Micron v. Vervain
`IPR2021-01548
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`3. Ultra-MLC
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`Introduction
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`Although SLC flash is more endurable and provides better performance than MLC flash does,
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`cost is still an issue to users. What if we could have the best of the both worlds – a new gene
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`that delivers greater performance and endurance, but yet at the same time, is an economical
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`solution?
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`The answer is yes – Ultra MLC.
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`The very idea with Ultra MLC is that MLC flash consists of a number of fast and slow pages,
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`and only fast pages will be used for programming when using Ultra MLC. One can think of
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`Ultra MLC as an extended version of MLC flash. Table 1 and Figure 4 explain the concept of
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`Ultra MLC: The first and second bit of a memory cell corresponds to a fast and slow page,
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`respectively, as shown in Table 1 (Left). Since we program fast pages with Ultra MLC, only
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`the bits highlighted in red in Table 2 (Middle) will be used.
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`Table 1: Cell Content for MLC (Left), Ultra MLC (Middle) and SLC (Right), Respectively
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`When the two bit-sets (10 and 00) from MLC flash are discarded, the bit data from Ultra MLC
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`is almost identical to that with SLC flash. In Figure 4, the threshold voltage ranges that
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`correspond to 10 and 00 will be discarded, leaving the ones for 11 and 01. Differentiating the
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`amount of charges inside the floating gate becomes easier, since a more separate cell
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`distribution reduces the chance to misjudge the threshold voltage for each cell.
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`4
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`Figure 4: Cell Distribution vs. Threshold Voltage for Ultra MLC
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`www.advantech.com
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`Vervain Ex. 2002, p. 6
`Micron v. Vervain
`IPR2021-01548
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`Advantage(s)
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`Advantage(s)
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`Description(s)
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`Ultra MLC
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`Performance
`enhancement
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` Only fast pages are programmed with Ultra MLC flash and
`therefore the write performance is improved.
`Please refer to "Section 4: Performance" for details.
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`Lifespan
`extension
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` Ultra MLC's endurance is better than that of MLC by at least 15X.
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`Please refer to "Section 5: Endurance" for details.
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`Cost-effective
`solution
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`The characteristics of Ultra MLC are similar to that of SLC flash,
`but Ultra MLC is a much more economical solution cost-wise.
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`Table 2: Major Advantages of Ultra MLC
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`4. Performance
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`Observations
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`5
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`Figure 5: Read/Write Performance for CF with PS3016-P8
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`With the same usable capacity of the SSD, the sustained write performance has been
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`obviously improved, and the read performance with ultra MLC is also comparable to that
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`with SLC one.
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`www.advantech.com
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`Vervain Ex. 2002, p. 7
`Micron v. Vervain
`IPR2021-01548
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`5. Endurance
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`Testing Methodology
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`Observations
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`6
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`Figure 6: Endurance Comparison among SLC, MLC and Ultra MLC
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`We program and erase only one block at a time until it becomes unusable (later bad block)
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`and then move on to the second block so on and so for.
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`In Figure 6, it is obvious to see that Ultra MLC outperforms MLC in terms of withstanding a
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`greater amount of usage. In general, MLC endurance is considered to be about 3K times, and
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`our previous experiments have allowed us to conclude that endurance of Ultra MLC is at least
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`15 times greater than that of MLC.
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`Appendix A displays the ECC values based on the three types of flash. Since MLC consists of
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`four voltage levels, the chance of one bit interfering the other becomes greater, which could
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`be translated into a higher ECC value. Therefore with MLC flash, a controller’s ECC-ability
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`needs to be more robust.
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`On the contrary, SLC and Ultra MLC have only two voltage levels and the possibility of
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`bit-interference becomes less, which could be observed from a lower ECC value in Appendix
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`A.
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`www.advantech.com
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`Flash Type vs. Endurance
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`200000
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`180000
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`160000
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`140000
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`120000
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`100000
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`80000
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`60000
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`40000
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`20000
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`0
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`Write/Erase Cycles
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`1
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`2
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`3
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`4
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`5
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`6
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`7
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`8
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`9
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`10
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`11
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`12
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`13
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`14
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`15
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`16
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`17
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`18
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`Bad Block
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`SLC
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`MLC
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`ULTRA MLC
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`Vervain Ex. 2002, p. 8
`Micron v. Vervain
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`6. Conclusion(s)
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`Ultra MLC, a part of the MLC family has been proved to provide better performance and
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`greater endurance by programming only fast pages. Our experiment has shown that the
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`read/write performance is improved. Additionally, endurance of Ultra MLC is at least ten times
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`greater than that of MLC, which is used by programming both fast and slow pages. We
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`believe that Ultra MLC is the most economical alternative for Industrial NAND flash
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`applications when it comes to stable and cost-efficiency requirements.
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`7
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`Advantech Co., Ltd. –Founded in 1983, Advantech delivers visionary and trustworthy industrial
`computing solutions that empower businesses. We cooperate closely with solution partners to provide
`complete solutions for a wide array of applications in diverse industries, offering products and solutions
`in three business categories: Embedded ePlatform, eServices & Applied Computing, and Industrial
`Automation groups. With more than 3,400 dedicated employees, Advantech operates an extensive
`support, sales and marketing network in 18 countries and 39 major cities to deliver fast time-to-market
`services to our worldwide customers. Advantech is a Premier Member of the Intel® Embedded and
`Communications Alliance, a community of embedded and communications developers and solution
`providers. (Corporate Website: www.advantech.com). Copyright
`Copyright© 2010 Advantech Co., Ltd. All rights reserved.
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`www.advantech.com
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`Vervain Ex. 2002, p. 9
`Micron v. Vervain
`IPR2021-01548
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`Appendix A
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`
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`SLC
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`MLC
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`Ultra MLC
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`Endurance Max ECC Failure Type
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` Endurance Max ECC Failure Type
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` Endurance Max ECC Failure Type
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`130420
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`154682
`146872
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`173730
`
`169906
`134393
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`192340
`
`0
`
`0
`0
`
`0
`
`0
`0
`
`0
`
`Erase Fail
`
`Erase Fail
`Erase Fail
`
`Erase Fail
`
`Erase Fail
`Erase Fail
`
`Erase Fail
`
`
`
`
`
`
`
`
`
`
`
`
`
`31132
`
`61588
`52286
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`63206
`
`56847
`54888
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`52543
`
`60782
`58269
`
`10
`
`18
`9
`
`19
`
`15
`14
`
`10
`
`17
`12
`
`Erase Fail
`
`Erase Fail
`Erase Fail
`
`Erase Fail
`
`Erase Fail
`Erase Fail
`
`Erase Fail
`
`Erase Fail
`Erase Fail
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`100261
`
`84238
`104283
`
`116143
`
`108135
`106080
`
`112328
`
`137423
`120583
`
`0
`
`0
`0
`
`0
`
`0
`0
`
`0
`
`0
`0
`
`Erase Fail
`
`Erase Fail
`Erase Fail
`
`Erase Fail
`
`Erase Fail
`Erase Fail
`
`Erase Fail
`
`Erase Fail
`Erase Fail
`
`0
`0
`
`0
`
`0
`0
`
`0
`
`1
`0
`
`0
`
`0
`0
`
`Erase Fail
`Erase Fail
`
`Erase Fail
`
`Erase Fail
`Erase Fail
`
`Erase Fail
`
`Erase Fail
`Erase Fail
`
`Erase Fail
`
`Erase Fail
`Erase Fail
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`60128
`
`50923
`39572
`
`51206
`
`62755
`39284
`
`42756
`
`52931
`30845
`
`149203
`139485
`
`158384
`
`139575
`153753
`
`142934
`
`119374
`194743
`
`128475
`
`158222
`120384
`
`
`
`
`9
`
`8
`19
`
`14
`
`13
`11
`
`9
`
`14
`21
`
`Erase Fail
`
`Erase Fail
`Erase Fail
`
`Erase Fail
`
`Erase Fail
`Erase Fail
`
`Erase Fail
`
`Erase Fail
`Erase Fail
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`135190
`
`122059
`140787
`
`130579
`
`120857
`102394
`
`101495
`
`90572
`99184
`
`0
`
`0
`0
`
`0
`
`0
`1
`
`0
`
`0
`0
`
`Erase Fail
`
`Erase Fail
`Erase Fail
`
`Erase Fail
`
`Erase Fail
`Erase Fail
`
`Erase Fail
`
`Erase Fail
`Erase Fail
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`8
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`www.advantech.com
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`Vervain Ex. 2002, p. 10
`Micron v. Vervain
`IPR2021-01548
`
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