TABLE OF CONTENTS This chapter discusses how completed die are tested. The chapter describes the validation of the design, the root causes and the fixing of design bugs, and the testing flow to identify manufacturing defects.
Upon completion of this chapter the reader will be able to:
Understand the importance of design for test (DFT) circuits.
Understand how scan sequentials are used.
Describe the different types of silicon bugs.
Understand how a shmoo diagram is used in debug.
Describe some of the tools used in silicon debug.
Describe the different ways of fixing silicon bugs.
Understand the silicon test flow used to identify manufacturing defects.
The most exciting single day in the life of any semiconductor product is first silicon, the day when the first chips complete fabrication. This day comes after what may have been years of simulation and is a suspenseful test of whether anything crucial has been overlooked in the design or fabrication of the product. Some of these first chips are immediately packaged and plugged into circuit boards for testing. While engineers cross their fingers and hold their breath, the product is powered up for the first time. In the best scenario, the chips may behave exactly as simulations predicted they would. In the worst case, the only result of applying power may be smoke from a suddenly melting circuit board. Most first silicon designs fall somewhere between these extremes, being somewhat functional but not behaving exactly as expected. Silicon debug and test is the...
