Focused ion beam in-situ cross sectioning and metrology in lithography

Jesse A. Salen; Drew Barnes; Gregory J. Athas; Neil J. Bassom; J. David Casey Jr.; Kathryn E. Noll; Don E. Yansen

doi:10.1117/12.361311

3 September 1999 Focused ion beam in-situ cross sectioning and metrology in lithography

Jesse A. Salen, Drew Barnes, Gregory J. Athas, Neil J. Bassom, J. David Casey Jr., Kathryn E. Noll, Don E. Yansen

Proceedings Volume 3882, Process, Equipment, and Materials Control in Integrated Circuit Manufacturing V; (1999) https://doi.org/10.1117/12.361311
Event: Microelectronic Manufacturing '99, 1999, Santa Clara, CA, United States

Abstract

We demonstrate an approach to cross-section and measure sub- 0.25 micrometer photoresist profiles in both a manual and an automated fashion. This approach includes the use of a focused ion beam (FIB) system to cut small trenches through photoresist lines, leaving a clean, vertical face to measure. We demonstrate the advantage of using this process over existing techniques in the semiconductor industry. A FIB can locally cross-section the photoresist, resulting in a side- wall that is comparable to that of a mechanical cleave. It can then measure the profile of the photoresist at multiple points using a 5 nm gallium probe. The system accomplishes the entire process inside one vacuum chamber with a limited number of steps. In contrast, when using a SEM to measure profiles, the sample must be mechanically cleaved outside of the vacuum chamber, potentially destroying the entire part and leaving a slightly distorted viewing face. Also, a SEM probe can cause swelling of the photoresist due to higher currents and penetration depths than a FIB probe and must therefore be used at low accelerating voltages. When operated at these low accelerating voltages, the SEM has degraded resolution with a spot size near 10 nm. A scanning probe microscope (SPM), on the other hand, can non-destructively measure profiles, but it is slow and less automated than the FIB or SEM. Unlike a FIB, the SPM lacks the ability to image the material transition directly beneath the photoresist. We also address concerns of sample damage, gallium contamination, and image quality.

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Jesse A. Salen, Drew Barnes, Gregory J. Athas, Neil J. Bassom, J. David Casey Jr., Kathryn E. Noll, and Don E. Yansen "Focused ion beam in-situ cross sectioning and metrology in lithography", Proc. SPIE 3882, Process, Equipment, and Materials Control in Integrated Circuit Manufacturing V, (3 September 1999); https://doi.org/10.1117/12.361311

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KEYWORDS

Photoresist materials

Gallium

Scanning electron microscopy

Contamination

Ions

Metrology

Imaging systems

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