Ultraviolet Raman stress mapping in silicon
Abstract
We report micro-Raman stress imaging in silicon structures using 351 nm excitation. This excitation has an extremely shallow optical penetration depth (≈5 nm) in silicon. It should also ultimately provide higher spatial resolution compared to visible wavelengths used in micro-Raman studies. As a test we examine a wafer which consists of a patterned nitride/polycrystalline silicon/oxide/substrate "stack" with neighboring regions of device-quality silicon covered only by a thin oxide layer. We obtain two-dimensional images with spatial resolutions ranging from 1 to 4 μm. The smallest Raman shift reliably detectable is found to be ±0.07 cm-1, corresponding to a stress magnitude of 35 MPa. Stresses on the order of 140 MPa are observed beneath the stack region. The contrasting linewidths between the substrate and polycrystalline silicon provide a complementary image.
- Publication:
-
Applied Physics Letters
- Pub Date:
- April 1999
- DOI:
- 10.1063/1.123729
- Bibcode:
- 1999ApPhL..74.2008H
- Keywords:
-
- 81.05.Cy;
- 78.30.Am;
- 78.40.Fy;
- 81.70.Fy;
- Elemental semiconductors;
- Elemental semiconductors and insulators;
- Semiconductors;
- Nondestructive testing: optical methods