Impact of wet ceria abrasive size on initial step height removal efficiency for Isolated SiO 2 film chemical mechanical
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Journal of the Korean Physical Society https://doi.org/10.1007/s40042-020-00022-w
ORIGINAL PAPER
Impact of wet ceria abrasive size on initial step height removal efficiency for Isolated SiO2 film chemical mechanical planarization Sang‑Su Yun1 · Jea‑Gun Park1,2 Received: 2 November 2020 / Revised: 11 November 2020 / Accepted: 16 November 2020 © The Korean Physical Society 2020
Abstract In 3-dimensional memories such as NAND flash and cross-point memory, the integration fabrication processes face a notable initial-step-height of an isolated S iO2-film deposition, which is an extremely critical process removing such initialstep-height perfectly via chemical mechanical planarization (CMP). The S iO2-film polishing-rate difference was generated between upper and lower locations of initial-step-height and was evidently depended on the nano-ceria abrasive size in an isolated SiO2-film CMP slurry; that is, the polishing ratio of the upper location to lower location remarkably increased from 4.5:1 to 11.5:1, as the ceria abrasive size increased from 21.3 to 81.0 nm. The difference of polishing rate was associated with a local pressure difference between upper and lower locations of initial-step-height; that is, the local pressure at the upper location remarkably increased from 5.2 to 14.2 PSI, while it at the lower location very slightly decreased from 1.0 to 1.3 PSI, as the ceria abrasive size increase from 21.3 to 81.0 nm. Thus, a larger ceria abrasive size in an isolated SiO2-film CMP slurry led to better removal ability (i.e., a shorter polishing time of initial-step-height and a thicker remaining isolated SiO2-film thickness). Keywords CMP · CMP slurry · Isolated SiO2-film · Initial step height · Ceria abrasive size
1 Introduction Recently, 3-dimenstion (3D) NAND flash memory, being fabricated with vertically stacked charge-trap memory-cells, has been rapidly scaled down beyond 128 memory-cells [1–3]. In addition, 3D cross-point memory, being fabricated with vertically stacked phase-change-memory-cells and chalcogenide based selectors, has been reported to open a new memory area that covers the interface between dynamic-random-access memory and 3D NAND Flash memory [4–6]. The fabrication of such 3D memories produces indispensably a high initial-step-height of an isolation film (e.g., S iO2), Supplementary Information The online version contains supplementary material available at https://doi.org/10.1007/s4004 2-020-00022-w. * Jea‑Gun Park [email protected] 1
Department of Electronics and Communications Engineering, Hanyang University, Seoul 04763, Republic of Korea
Department of Nanoscale Semiconductor Engineering, Hanyang University, Seoul 04763, Republic of Korea
2
as shown in Fig. 1a. A chemical–mechanical-planarization (CMP) process of an isolated film should be essentially necessary for planarizing a high initial-step-height, generally performed using nano-ceria abrasive-based CMP slurry [7–10]. Ideally, the CMP process should produce a perfect planarization by polishing only the
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