I. INTRODUCTION: PROCESS VARIABILITY
A significant challenge for both design and test is imposed by process variability.
For example, a representative 65nm transistor has a gate oxide thickness of 1.3 nm. Given a molecule of is about 0.3 nm the oxide thickness consists of only 4 or 5 molecules
II. LIMITATIONS OF TRADITIONAL TEST
III. WHAT IS ADAPTIVE TEST?
Adaptive Test is a broad term used to describe methods that change test conditions, test flow, test content and test limits based on manufacturing test data and statistical data analysis.
Included in the definition is feed-forward from inline test and early test steps to later test steps and feed-back data from post-test statistical analysis of later test steps that is used to optimize earlier steps.
(page 2)
A high-level flow diagram of Adaptive Test is shown in Fig. 1 (adapted from [5]).
IV. DEVELOPMENT OF ADAPTIVE APPROACHES
Some of the earliest developments in adaptive methods were concerned with Iddq test, where it became evident that a fixed threshold approach was ineffective, given the large variations seen in leakage current from die to die (Maxwell et al. [7]).
(page 2 col 2)
Developments such as the above gave rise to the concepts of outlier screening and “data driven” testing
More recently adaptive approaches have been applied to analog circuits
V. STAGES OF ADAPTIVE TEST
C. Future Methods - Complex Adaptation
(page 3)
B. Emerging Methods - Simple Adaptation
Many of these have already been described as outlier detection methods
C. Future Methods - Complex Adaptation
The concept of a static algorithm can be extended to incorporate a “DUT response model”.
The more likely outcome is DUTs are identified as members of a common sub-group and the test flow is dynamically adjusted using the group of DUTs and their common response.
VI. BENEFITS OF ADAPTIVE TEST
A. Lower Test Costs
Test time reduction is a major benefit.
Test costs are also lowered by reducing test time
p5
B. Better Quality and Reliability
