Investigation of stress in shallow trench isolation using UV micro-Raman spectroscopy

We present an investigation of local mechanical stress in shallow trench is olation by UV micro-Raman spectroscopy. UV light (364 nm) penetrates only 1 5 nm into silicon. In contrast to conventional micro-Raman spectroscopy usi ng visible light only the stress very close to the surface is monitored. In this way, local areas of high stress can be detected, that are not seen wi th longer wavelength light due to averaging. We demonstrate the advantages of the UV method by an investigation of the influence of different trench o xide densification ambients on the amount of mechanical stress in the silic on substrate. We find, that large mechanical stress up to 800 MPa is introd uced at the active area edges during densification in steam ambient. This s tress is caused by the formation and growth of a bird's beak, which may lea d to defect creation especially in small trenches. This investigation demon strates the capability to use UV micro-Raman spectroscopy in ULSI technolog y. (C) 2001 Elsevier Science Ltd. All rights reserved.