The influence of processing on wafer alignment is becoming an increasingly important issue. We need to improve an
overlay accuracy and alignment performance when design rule are reduce. Especially, the alignment of Metal layers
gets some process effects, then we should have prepared to prevent alignment error by the wafer loss and reducing
Alignment of Metal 0 layer in the local interconnect integration is much affected by ILD thickness, resist coating
process, but also there are effective phase depth.
In this paper, new alignment strategy is presented by simulation of stack structure impact on alignment. We are able
to accomplish the increase of alignment signal intensity by new alignment strategy. In addition, we can be achieved
alignment robustness to process variation for M0 to M0C alignment of local interconnect.
As reduction of k1 factor continues, it becomes more extensive to apply resolution enhancement techniques (RETs) such as phase shift mask (PSM), optical proximity correction (OPC) and off axis illumination (OAI). OPC has been playing a key role to control of pattern printing accuracy and maximize the overlapping process window especially for logic devices. However, RETs, including OPC, tend to increase the sensitivity of printed images to the projection lens aberrations. In order to improve the pattern uniformities and image qualities, lens aberration should be considered as one of the most important factor to OPC modeling. In this paper, we investigated the impact of lens aberration on data set for OPC model generation. The data of projection lens aberrations on exposure tools were extracted by LITEL In-situ Interferometer (ISI) and the sensitivity of CD variation with each lens aberration was simulated by SIGMA-C Solid-E Simulator. Among the lens aberrations, the significant error sources contributing to setting a limit to use one general OPC model with multiple exposure tools were analyzed. Also, the lens aberration specification to use one general OPC model was proposed. By considering the effect and specification of lens aberrations, further improvement of the OPC model accuracy and prevention of device yield loss originated from lens aberrations are expected.
As via first scheme is employed for dual damascene patterning, via filling process has been posed many challenges to the patterning process. For organic BARC assisted dual damascene patterning, differences in etch selectivity between the organic BARC and ILD material generate fence defect problems. It is highly improbable that organic BARC film remains thick enough to protect the via bottom. To reduce the negative impact on the substrate, the BARC material requires to fill small vias. In addition, anti-reflective behavior for KrF lithography, comparable dry-etching and high wet-etching selectivity to the ILD, and compatibility with photoresist processing are necessary for a successful dual damascene patterning. A sacrificial, spin-on 248nm UV absorbing organosiloxane based inorganic BARC has been developed to meet these needs. Inorganic BARC is a material that fills the vias and reduces iso-dense bias for both fill and top coverage and hole-free substrate at trench lithography.
In this paper, the comparison of the performance of inorganic BARC and organic BARC assisted dual damascene patterning with low-k dielectric was conducted. We evaluated the performance of inorganic BARC in terms of the via fill capability, depth of focus, exposure latitude, etch selectivity and etch profile results. The reduction of iso-dense bias from via filling with inorganic BARC instead of organic BARC is discussed.
We investigated the influence of lens aberration on the lithographic performance according to the phase error and topography effects of phase-shift mask (PSM). Twin-bar and isolated pattern showing high sensitivity to lens aberration were used for this study. The simulation of aberrated images was carried out using the Solid-CTM simulator. Specially, we quantified the relationship between patterning behaviors such as the isofocal tilt, the left-right (L-R) CD difference and the Z7 and Z9 individual Zernike coefficients. Isofocal tilt aberration sensitivity for Z9 was 0.4nm/nm, which resulted in 2nm CD variation using lens with 5nm Z9 value. When using the lens with 5nm Z7 value, the L-R CD difference and its sensitivity are 10nm and 2nm/nm, respectively. Finally, we evaluated the patterning performance by phase error effect, and determined the phase error criteria for PSM. The pattern placement error was increased by increasing phase error as well as Z7 value, while its slope to the defocus was similar regardless of lens aberration. However, it was found that the aberration sensitivity was not affected by phase error. The simulation predicted that the sensitivity of lens aberration could be increased due to mask topography effect. The nominal shift of phase edge attributed to mask topography was measured.