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As the process technology continues to scale, the stability of embedded Static Random Access Memories (SRAMs) is a growing concern in the design and test community [1–3]. Maintaining an acceptable Static Noise Margin (SNM) in embedded SRAMs while scaling the minimum feature sizes and supply voltages of the Systems-on-a-Chip (SoC) becomes increasingly challenging. Modern semiconductor technologies push the physical limits of scaling which results in device patterning challenges and non-uniformity of channel doping. As a result, precise control of the process parameters becomes exceedingly difficult and the increased process variations are translated into a wider distribution of transistor and circuit characteristics.

Large SRAM arrays that are widely used as cache memory in microprocessors and application-specific integrated circuits can occupy a significant portion of the die area. In an attempt to optimize the performance/cost ratio of such chips, designers are faced with a dilemma. Large arrays of fast SRAM help to boost the system performance. However, the area impact of incorporating large SRAM arrays into a chip directly translates into a higher chip cost. Balancing these requirements is driving the effort to minimize the footprint of SRAM cells. As a result, millions of minimum-size SRAM cells are tightly packed making SRAM arrays the densest circuitry on a chip. Such areas on the chip can be especially susceptible and sensitive to manufacturing defects and process variations. International Technology Roadmap for Semiconductors (ITRS) [4, 5] predicted “greater parametric yield loss with respect to noise margins” for high density circuits such as SRAM arrays, which are projected to occupy more than 90% of the SoC area in the next 10 years (Figure 1.1).

Keywords

Test Time Table SRAM Cell Automate Test Equipment Technology Scaling March Test 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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© Springer Science + Business Media B.V 2008

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