Invited Paper VT-TuA3
The Importance of Vacuum Cleanliness in Semiconductor Process Control SEM Tools

Tuesday, October 23, 2018, 3:00 pm, Room 203B

In the semiconductor manufacturing process, integrated circuits are formed by many layers, and hundreds of process steps are required to produce a single wafer. If any problem occurs at any step of the production process, a huge amount of defective products will be produced. Therefore, inspecting the wafers during the production process is essential in order to discover any problem and solve it as early as possible.

Scanning electron microscopes are playing an important role in process control and yield management of the semiconductors process. Defect review (DR) SEMs are used for defect identification, review and classification, enabling the semiconductor fabrication plant (fab) yield management system to identify failures or problems at an early stage in the process flow and to point on possible root cause. The Critical Dimension (CD) SEM is used to measure critical dimensions of the fine patterns formed on the semiconductor wafer, enabling verification of process quality. Since the SEM tools are in-line tools it is essential that they will not affect the scanned wafer.

Organic contamination is one of the main challenges in vacuum systems and hence in e-beam based metrology systems. Organic molecules adsorbed on the wafer surface during SEM inspection may cause yield loss in the following process steps or affect the CD measurement. In addition, with decrease in design rules the processes become more and more sensitive to organic contamination and therefore the ability to control vacuum cleanliness is crucial. In this paper, we will specify some of the challenges involved in the design of clean SEM based metrology tools, possible contamination sources and possible effects of such contamination molecules on the wafer.