Cu/low S
P
E
C
I
A
L
F
O
Îş C
U
S
Time-to-Detect Frames the Integrated Debate Ralph Spicer, Dadi Gudmundsson, and Raman Nurani, KLA-Tencor Corporation
Is integrated defect inspection really the wave of the future? Analysis shows that a simple particle detection strategy is unlikely to be more cost effective than a comprehensive excursion inspection strategy, even if the particle detection can be integrated to a process tool.
The decision whether or not to integrate defect inspection onto process tools is one of the most important decisions facing 300 mm fab planners. This decision impacts everything from capital procurement strategies, to automation, to floor-planning, to data systems integration. And, once made, this decision is expensive, if not impossible, to change as the fab approaches first silicon. Therefore, it is important to understand the real variables behind this decision, moving beyond surface arguments that would appear to point strongly in favor of integration. This article discusses the relevant issues that must be analyzed when making decisions regarding the deployment of integrated versus non-integrated defect inspection in a new 300 mm fab.
significantly, making it vital to forecast such variables through several design rules before deciding on a strategy. When all of these considerations are taken into account, our analysis shows that the fact that particle detection can be integrated to a process tool does not necessarily make it the most cost effective strategy for 300 mm fabs. Trends affecting the decision
In order to determine whether or not an integrated inspection strategy makes sense for the fab, it is important to understand the variables that drive yield losses, and how technology trends are affecting these variables.
CYCLE TIME Cueue Times Automation
Layout
The decision to integrate
Recent arguments for integration cite equipment productivity as the driving variable upon which the decision should be based. While this is an important factor, it is also important to consider variables that drive yield, such as process tool excursion frequencies, defect kill probabilities, and the detection capability of the integrated and non-integrated systems being considered, as illustrated in Figure 1. Furthermore, while productivity-related variables remain relatively constant through design rule generations, the yield-related variables scale 42
Winter 2002
Yield Management Solutions
STEP YIELD
PROCESS DEVELOPMENT
Excursion Defect Frequencies Types Kill Probabilities
Yield Learning Support Design Rule Extendabilty
INSPECTION TECHNOLOGY
PROCESS TOOL OUTPUT Floor Orocess Tool Space Productivity Reliability
Inspection Strategy Decision
False Inspector Alarm Detection Capability Excursion Rate Time to Decision
Fastest Ramp Highest Yard Minimum Cycle Time
Figure 1. A multitude of factors must be considered when deciding on an inspection strategy for a 300 mm fab. These include productivity factors such as cycle time and process tool output, and yield factors such as step yield, process development, and the capabilities of the inspection technology.