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Monday, January 7, 2008

Flash Memory Basics

What's the anatomy of a memory card?



 


The flash memory that you load into your camera is something most of us take for granted, but these little devices are one of the most important elements in the entire imaging system. The latest cards are packed with high-tech features and technology.
There are a few examples of cards without controllers (e.g., SmartMedia and early versions of the xD Picture card) that have had severe legacy issues. Every time a higher-density card was introduced, the camera companies would have to issue new firmware updates for the cameras in order to support the new card sizes. This implied that the cameras were designed to support firmware updates and that the camera companies were still interested in supporting older products. This may be something we take for granted today, but I still have examples of cameras I worked on early in my career, which support SmartMedia cards up to only 8 MB.

New controller-based memory cards have the latest and greatest firmware programmed in the controller. As bigger and faster cards are introduced, most legacy issues can be addressed automatically without requiring a change in the camera firmware.

In The Beginning, There Were Wafers
As important as controller chips are, they play a fairly minor role in the overall cost structure of the card. The real money is in the NAND flash chips. Flash memory is a commodity product manufactured by less than 10 semiconductor companies around the world. Samsung, Toshiba, SanDisk, Hynix, Intel and Micron are, by far, the largest manufacturers. Like pork bellies, oil and coffee, the daily prices are driven by supply and demand, but the fundamental cost structure of flash is based on the cost to produce a semiconductor wafer and the yield of good die from each wafer.

It's that simple: the more usable chips you can yield, the lower the cost per chip and the better your cost structure can be.
As important as controller chips are, they play a fairly minor role in the overall cost structure of the card. The real money is in the NAND flash chips. Flash memory is a commodity product manufactured by less than 10 semiconductor companies around the world. Samsung, Toshiba, SanDisk, Hynix, Intel and Micron are, by far, the largest manufacturers.

Samsung is the largest of the NAND flash manufacturers. Its most modern production lines currently produce NAND flash on 12-inch (300mm) wafers using a 53 nanometer process. This means that it's able to space the transistors at a 53 nanometer pitch or 53/1,000,000,000 of a meter. Samsung is currently improving this process technology at a 12-month pace, allowing it to double the density of its chips every year. That's why we see the densities consistently increasing while prices continue to fall.


 

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