E-beam Inspection System Research Articles

Alternative voltage-contrast inspection for pMOS leakage due to adjacent nMOS contact-to-poly misalignment

We propose an innovative voltage-contrast (VC) inspection approach for detection and verification of the process window for contact-to-poly overlaying. The method uses alternative scans for inline detection of leakage induced by underneath overlay drift. Conventional optical inspection with box-in-box or bar-in-bar test structures cannot accurately indicate the overall overlay performance for all chip locations as geometries continue to shrink. An e-beam inspection system with VC contrast imaging was introduced during a recent technology update. The alternative e-beam system with positive and negative charging modes was set up to perform dual scans for sensitive pMOS and nMOS detection. Although positive-mode scanning can detect pMOS leakage on the surface, it indicates a normal subsurface with no leakage. Defects can only be identified by another scan in negative mode to detect contact-to-poly misalignment in the neighboring nMOS. Leakage electrons affect each other as they spread through poly lines crossing p/nMOS. The principle and mechanisms for leakage defects were verified in a series of corrective actions for misalignment. The methodology allows inline detection instead of end-of-line electrical testing and de-layered analysis. This greatly shortens the response time and facilitates yield learning.

Process Optimization of Contact Module in NOR Flash Using High Resolution e-Beam Inspection

The inspection sensitivities and capture rate capabilities of high resolution e-beam inspection system with extracting and retarding mode are evaluated. E-beam with retarding mode inspection demonstrates better performance and reflects the wafer sort yield loss in contact failure items directly. After the contact module process optimization, the yield was improved almost two times above.

Voltage Contrast Inspection Methodology for Inline Detection of Missing Spacer and Other Nonvisual Defects

A test structure specifically designed to allow inline detection of missing spacer is introduced. Missing spacer is too small to be physically detected with any current inspection tool and therefore its existence must be flagged using voltage contrast for detection with an e-beam inspection system. The structure and methodology used to address this defect during the ramp of a recent technology is described. Key benefits include a dramatically faster learning cycle and much better signal-to-noise ratio for split experiment evaluation. Missing spacer is one example of a growing class of nonvisual defects which will greatly impact future semiconductor technologies. General principles for designing test structures to detect these defect types are discussed.

Patterned wafer defect density analysis of step and flash imprint lithography

Acceptance of imprint lithography for complementary metal-oxide semiconductor (CMOS) manufacturing will require demonstration that it can attain defect levels commensurate with the requirements of cost-effective device production. This article specifically focuses on this challenge presenting the current status of defect reduction in step and flash imprint lithography (S-FIL). The results of defect inspections of wafers patterned using S-FIL are summarized. The masks or templates used to imprint wafers for this study were designed specifically to facilitate automated defect inspection. The templates were made by employing CMOS industry standard materials and exposure tools. The primary wafer inspection was performed using a KLA Tencor-2132 (KT-2132) automated patterned wafer inspection tool. Additional imprint inspections were carried out on a KT-eS32 e-beam inspection system. The first section of the article provides a brief background of S-FIL technology. Next, the defect types and potential sources are described. Section III contains recent results demonstrating defect reduction below 5cm−2 and the result of a high resolution e-beam inspection that provide insight into sub-50-nm S-FIL specific defects. A brief summary concludes the article.