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EETE FEBRUARY 2013

From ROM to Flash for added flexibility By Björn Scharfen Restrictions of ROM-Based technology require new memory concepts. Until now, data were saved on a chip card with security controllers based on ROM and EPROM memory technology. However, conventional Mask ROM technology is approaching its limits. Miniaturization of chip structures results in disproportionately increased mask costs. Furthermore, Mask ROM technology does no longer meet market requirements with regards to increasingly differentiated smart card functionalities. On the other hand, Flash products offer a shorter time-to-market by avoiding process time in the semiconductor production. In addition Flash products allow product customization to happen at a later stage in the value chain, i.e. card manufacturers can decide prior to shipment of the card which operating system and application code to be programmed into the Flash devices depending on the project and market requirements. This offers a significant higher flexibility compared to ROM mask products, whereas typically each project requires a specific mask and the total production process down to the semiconductor fabric needs to be carefully planned. With its Solid Flash security controllers, Infineon Technologies combines the advantages of a flexible and reliable Embedded Flash technology with high performance and certified security for the use in contact-based or contactless chip card applications. Solid Flash therefore combines the more flexible Flash memory technology with a sophisticated security mechanism that may be even superior to those of Mask ROM products. Whereas it takes several weeks with ROM products to apply a new code it can be done immediately with Solid Flash products and no compromises needs to be made on security. NVM cell used for Solid Flash The current Flash memory used at Infineon is based on the UCP (Uniform Channel Program) concept and has been in use for almost 10 years, proven in safety-critical automotive and SIM card applications. In smart card generations down to the 130nm node, it was mainly used in combination with ROM: ROM for the code storage and UCP initially replaced the outdated EPROM concepts for storage of the data. For Solid Flash products in 90nm the UCP concept is also used for code storage, combining the benefits of Flash and EEPROM in one technology. The small cell size allows an economical implementation and specially contactless or dual Interface cards benefit from the fast cell access and the low power consumption. The way from masked ROM to Flash Historically commercial reasons demanded for a mix of ROM and EEPROM technology in smart card products. Even 10 years ago a footprint ratio of about 4:1 per stored bit led to a configuration of 4kB EEPROM and 80kB of ROM for a typical controller in payment applications. Thus, the combination of ROM to store constant program code and EEPROM for application data has yielded a cost effective combination of both technologies in smart cards. With the introduction of smaller technology nodes, the area footprint of Flash has reduced considerably to a point whereby the total cost of ownership for a ROM in comparison with Flash has to be carefully analyzed. The costs for ROM masks significantly increase with every smaller technology step of silicon geometry, e.g for a 65nm technology they are over 10 times higher than with a 220nm process. In addition, as the size of the chip gets smaller and the wafer size increases towards 300mm, the minimum order quantities of a customer specific ROM mask product of a smaller geometry chips on a larger wafer will increase to a non-economical figure and go up to a million of pieces per lot. The threshold where it does make sense to move towards Flash depends on the overall memory size as well as on the chip size. In other applications such as automotive and security controller for SIM Cards this threshold Dipl.-Wirtsch.-Ing. (FH) Björn Scharfen, Marketing Director, is heading the product marketing and management of the Secure Mobile & Transaction Business Line at Infineon – www.infineon.com www.electronics-eetimes.com Electronic Engineering Times Europe February 2013 31


EETE FEBRUARY 2013
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