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SDRAM Factory Schematics: Back End and Front End Factories

As illustrated in Figure 1, the manufacturing process of SDRAMs can be divided in two parts:

  • Front End (FE)
  • and Back End (BE).

The FE is the part of the manufacturing where the work is done on the wafer level, whereas in BE the work is done at chip and module levels. According to this classification also the so called FE and BE factories can be distinguished. FE and BE factories can be on the same or on different locations.

Sdram Factory Schematics

Figure 1: Schematic representation of a SDRAM factory

The FE production is divided in two parts:

  • Wafer Level Processing
  • and Wafer Level Test.

Wafer Level Processing includes all microelectronic processes which are needed to make the chips. Wafer Level Test, as the name tells, is a test procedure aiming to find out the bad chips and thus assuring that only good chips will be sent in BE for father processing.

The BE is divided in four parts:

At Chip Level Assembly the wafers are cut into single chips. After this procedure lead pins are attached to the chips and the chips are molded into a special plastic compound. Due to the fact that during these procedures the chip is subjected to mechanical and thermal stress, a new test at the chip level is required - Chip Level Test or also called Back End Test. The chips which survive the Chip Level Test will be selected for Module Assembly. Finally the modules have to pass the so called Module Test and Module Application Test. If everything is Ok, the modules can be released for sale.