MEMORY TESTING METHODOLOGIES For embedded memory Minghuan Zhao

MEMORY TESTING METHODOLOGIES For embedded memory Minghuan Zhao 1

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Fault Characteristics � Address-Decoder Fault (AF) � Stuck-At Fault (SAF) � Transition Fault (TF) � Coupling Fault (CF) 3

Traditional solution � Walking Pattern-Complexity 2 N 2 � Sliding Pattern-Complexity 4 N 1. 5 � Butterfly Pattern-Complexity 5 Nlog. N � Means Size N Nlog. N N 1. 5 N 2 1 G 10. 5 sec 5. 3 min 4 days 366 years 4

Embedded memory Characteristics � embedded memory’s address, data, and control signals are usually not directly accessible through the I/O pins. 5

Solution: March && Memory Built-In-Self Test � March Test typically has complexity: O(N) �Linear access to memory by a specific order � Memory Built-In-Self Test(Architecture) Normal data in Model select Test clk reset Data generator Self-test controller Address Generator RAM Normal address Normal data out Reference Data receiver (Comparator) 6

March C-(evolved March C) March C- is a classical algorithm which is the foundation of other algorithms � { (w 0); (r 0, w 1); (r 1, w 0); (r 0, w 1); (r 1, w 0); (r 0)} � Complexity— 5 N=>O(N) � ascending order � descending order � r 0: read 0 � w 1: write 1 � March Element (w 0): M 0 � 7

{ (w 0); (r 0, w 1); (r 1, w 0); (r 0, w 1); (r 1, w 0); (r 0)} M 0 M 1 � � M 2 M 3 M 4 M 5 Address Fault, Transition Fault: M 2 and M 3 M 1 M 2 0 1 1 0 Stuck-At Fault: overwrite 0’s and 1’s M 2 1 0 1 0 8

{ (w 0); (r 0, w 1); (r 1, w 0); (r 0, w 1); (r 1, w 0); (r 0)} M 0 M 1 M 2 M 3 M 4 M 5 � Coupling Fault (CF) � j< i, Cj affected by Ci �M 1: Ci 1 ->0 falling behavior affect Cj �M 2: Ci 0 ->1 raising behavior affect Cj 0(j ) 1 2(i ) M 1 M 2 1 0 0 1 1 0 � j> i, detected by M 3 and M 4 9

Other March algorithm SAF AF TF CF MATS ALL Some MATS++ ALL March X ALL ALL Some March C- ALL ALL March A ALL ALL Some March B ALL ALL Some March Y ALL ALL Some 10

Challenge � Silicon area overhead � Complexity can be less than O(N) � Faults coverage � Decrease test instructions and data Model select Test clk reset Normal data in Data generator Self-test controller Address Generator Normal address RAM Reference Data receiver (Comparator) Normal data out 11