Scan Chain Diagnostics
Original Publication Date: 2008-May-05
Included in the Prior Art Database: 2008-May-05
Early yield monitoring and testing of critical circuit component such as storage element is very important for success of microprocessor/ASIC on cutting-edge semiconductor technology. The current known solution is to simpliy connect all the elements together seriesly by their pins. And then we can find out whether there is problem in these elements by scaning-in and scaning-out signal into this chain. The drawback is for different component types, size and etc, it has to redesign this test chain structure. This requires lots of time and effort. We invent an on-chip test structure. Its advantages are: 1) include a common frame for design component under test; 2) the common frame can be used for testing components with different sizes 3) the common frame can be used for testing components with different images; 4) high level test structure is fixed for different testing components; 5) flexiable test chain length: can test the whole chain or only subset of it ; 6) can easily mix different types of testing components to create more product-like environment for testing
Scan Chain Diagnostics
On Chip Test Structure
Ming Yin, Thomas Ludwig
Disclosed is a system for doing early circuit yield testing and monitoring critical circuit components. This invention uses a fixed-size and fixed-pin-location frame for different types of design components. So this on-chip test structure does not need to be changed for different types of design components. And also by using MUX, this on-chip test structure length can be changed by will.
The advantages of using this invention are:
It can be reused for components with different sizes, pin locations without high level test structure changes
Flexible testing structure length by using MUX
It can mix different types of testing components to create more product-like environment for testing and monitoring
Add dummy cells inside this frame for small-size components;
Large-size components will use 2 or more frames (in vertical direction)
In the Fig.1, this test structure has a single chain of design elements inside 4 columns. Every design element is represented by a frame. Only the first frame is shown as one example. Multiple different design elements can be easily mixed together inside one scan chain to have more product-like proximity around design elements. Since the frame's pin locations are not changed, high level test structure and signal/power routing do not need to be changed for different types of design elements. By using MUX we can easily skip part of scan chains in ca...