Investigation of stress-induced defects in shallow trench isolation by cathodoluminescence and Raman spectroscopies

Abstract

We have applied cathodoluminescence (CL) and Raman spectroscopies to shallow trench isolation (STI) processes in large scale integration to investigate crystalline defects and stresses by extracting the wafer after each process. A sample with high standby leakage current clearly showed dislocation-related luminescence lines (D lines) in the regions surrounding the memory cell. These regions contain various sizes of active and field areas ranging from 0.5to5μm. However, a normal sample showed no D lines in any region through the STI processes. The D lines were observed after liner oxidation, which was performed after trench patterning. Raman microprobe measurements showed that the trench patterning process generated a large inhomogeneous stress distribution up to 200MPa in the regions surrounding the memory cell. The inhomogeneous stress distributions caused by the trench patterning and the subsequent thermal processes are likely the main causes of dislocations. A comparison between the D lines in the CL spectra and the stress measured by a Raman microprobe clarified the mechanism of generation of crystalline defects. We can thus optimize the process conditions in STI processes by these spectroscopic methods.

Stress Field and Defect Evaluation with Shallow Trench Isolation Structure after Transistor Fabrication Processing by Raman and Cathodoluminescence Spectroscopies

“…Figure 4 shows the CL spectra of Si substrate detected at 18 K. Observed areas were STI structures with different width AA line on n+/p or p+/n. The most prominent peak around 1.1 eV (TO) is equivalent to the band-edge emission followed y a transverse optic (TO) photon emission [10]. In addition, faint peaks at 1.04 eV and 1.135 eV were observed, which might be induced by ion-implantation.…”

“…Thus, we attempted to evaluate stress fields after CMP and the transistor fabricating processing, applying Raman and CL spectroscopies. Moreover, CL spectroscopy is useful to detect some defects in Si substrates with a STI structure [10]. Therefore, in this study, we also attempted to estimate defects in the Si substrate after transistor fabrication because it is important to understand defects in the Si substrate.…”

Measurement of temperature-dependent stress in copper-filled silicon vias using polarized Raman spectroscopy

“…We can obtain the stress components r 0 11 and r 0 22 by measuring Dx 2 and Dx 3 in (x 0 , x 0 ) and (x 0 , y 0 ) configurations, respectively, and solving the simultaneous linear equations shown in Eqs. (8) and (9). Figure 5 shows the distribution of Dx 2 and Dx 3 measured in (x 0 , x 0 ) and (x 0 , y 0 ) configurations, respectively, at 298 K. The upward shift is observed only in the vicinity of the bottom and sidewall of the via in both configurations, while the downward shift is observed in almost all areas.…”

“…For example, the dislocations induced by the stress from a shallow trench isolation (STI) structure are known to cause junction leakage current. [4][5][6][7][8] Moreover, in three-dimensional (3D) stacked ICs connected by through-Si vias (TSVs), the reliability tends to decrease and the risk of failure increases because of their internal residual stress originating from their relatively complex manufacturing process.…”

Cathodoluminescence Microcharacterization of Recombination Centers in Lifetime-Controlled IGBTs

“…Although DLTS can clarify the energy level and the capture cross section of the defects, it is difficult to derive the spatial distribution. Cathodoluminescence (CL) is suitable for device characterization such as optoelectronic devices [8] and LSI devices [9]. In this paper, we applied cross-sectional CL measurements to the electron-irradiated IGBTs after annealing at 200-400 °C and discuss the relation between the static and dynamic electrical characteristics and the radiative recombination centers in the n-drift region.…”