TABLE OF CONTENTS Wafer fabrication and packaging are incredibly long and complex processes involving hundreds of demanding steps. These steps are never performed perfectly every time, and contamination and material variations combine to wafer loss in the process. Additionally, some of the individual chips on the wafers fail to meet customer electrical and performance specifications. In this chapter, the major yield measurement points are identified along with the major process and material factors that effect yield. Typical yields for the different yield points and for different circuits are presented.
Upon the completion of this chapter, you should be able to:
Name the three major yield measurement points in the process.
Explain the effect of wafer diameter, die size, die density, number of edge die, and defect density on the wafer-sort yield.
From a list of individual process step yields, calculate the accumulative fabrication yield.
Be able to explain and calculate an overall process yield.
Explain the four major influences on fabrication yield.
Sketch a yield-versus-time curve for different process and circuit maturities.
Explain the relationship between high process yields and device reliability.
Maintaining and improving process and product yields is the lifeblood of semiconductor manufacturing. To the casual observer, it would seem that the industry is fixated on production yields. It is. The demanding nature of the process and sheer number of processes required to produce a packaged chip result in product loss. These two factors result in a production...
