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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 elementary cell

As shown in Figure 1 a SDRAM elementary cell has two main parts:

  1. a transistor;
  2. and a capacitor;

The transistor plays the role of a switch and the capacitor is a place to store electrical charge. In order to store a physical “1” in a SDRAM cell the following processes take place:

  • Transistor opens
  • The charges/electrons are flowing and fill the capacitor
  • The transistor closes

SDRAM cross section view: stack vs. trench capacitor concepts

Technologically two DRAM concepts dominated the market till 2009:

  1. Stack capacitor concept (see a cross section in Figure 1)
  2. Trench capacitor concept (see Figure 2);

The last microelectronic companies which produced, but not producing anymore, DRAM chips based on the trench capacitor concept were Infineon Technologies, namely its daughter company Qimonda, Inotera Memories, Nanya Technologies and Winbond. The “rest of the DRAM world” (Samsung, Micron, Elpida etc.) produced and are still producing DRAMs based on the stack capacitor concept.

SDRAM Module Types

The following types of DRAM modules can be found in computers and notebooks: SIMMs, RIMMs, DIMMs and SODIMMs.

SDRAM Module Photos

The memory modules evolved parallel to the development of new processor generations. This is due to the fact that the processors have become faster and faster and the data quantity processed by them has expanded. Please see bellow examples of DRAM modules.

SDRAM Abbreviations

A list of most common abareviations used for SDRAM:

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