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Research Article

Preparation and Characterization of Ceria Abrasives for Semiconductor CMP from Cerium Carbonate Precursors

탄산세륨 전구체를 활용한 반도체 CMP용 세리아 제조

Suseong Jang1, Sohee Hwang2, Chung-Min Jeon4, Nam Soo Park5, Jae Young Jung6, and Woonjung Kim3

장수성1, 황소희2, 전청민4, 박남수5, 정재영6, 김운중3

1The master’s course, Department of Chemistry, Hannam University
2Doctor’s course, Department of Chemistry, Hannam University
3Professor, Department of Chemistry, Hannam University
4CEO, MS materials CO. LTD
5CMP General Manager, NNFC(National Nano Fab Center)
6Chief Technical Staff, Electronics and Telecommunications Research Institute
1한남대학교 화학과 석사과정
2한남대학교 화학과 박사과정
3한남대학교 화학과 교수
4엠에스머트리얼즈 대표이사
5나노종합기술원 CMP 총괄
6한국전자통신연구원 기술총괄
31 December 2025. pp. 109-124
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Abstract
반도체 집적회로 기술의 발전으로 미세 선폭과 다층 배선의 필요성, 엄격한 DOF(depth of focus)에 의해 CMP(chemical mechanical planarization) 공정이 다양하게 발전하고 있다. CMP 공정은 wafer를 pad에 밀착시킨 상태에서 수십~수백 nm 정도 크기의 입자를 가진 slurry를 패드에 분산시켜 산화막 또는 금속 박막의 화학적 반응을 유도함과 동시에 pad의 기계적 힘을 통해 wafer 표면을 평탄하게 하는 공정 중 하나이다. wafer의 polishing 과정에서 발생하는 결함은 링(ring), 스크래치(scratch), 존(zone), 반복(repeat)의 유형으로 분류할 수 있다. CMP 슬러리는 연마 입자, 분산제, 물과 기타 첨가제로 구성된 콜로이드성 용액이다. 연마 입자는 실리카(SiO2), 세리아(CeO2), 알루미나(Al2O3) 등이 사용되며, 필름이나 웨이퍼 재료 종류에 따라 이들 중 선택한다. 이 중, 세리아는 CMP 공정에서 낮은 입자 농도로도 높은 연마율(removal rate) 로 인해 주로 CMP 공정의 연마제로 사용된다. 연마 입자들을 분산시키고 입자 크기분포의 안정성을 높이기 위하여 보통 분산제를 사용한다. 분산제를 첨가함에 따라 슬러리의 입자 크기가 작아지고 분산제의 농도가 증가함에 따라 제타 전위(zeta-potential)가 큰 값을 가지게 되며, 전기적으로 안정화된다. 이 연구에서는 탄산세륨을 전구체로 하여 600~800℃ 온도에서 5시간 동안 소성하여 세리아 분말을 제조하였고, 해당 세리아 분말을 상용 D 분산제와 함께 수직 밀링 공정을 이용하여 슬러리를 제조하였다. 탄산세륨 전구체의 온도별 거동을 확인하기 위해 TGA 분석을 진행하였다. 온도별 세리아 분말의 특성을 평가하기 위해 색차계, SEM, TEM, XRD 분석을 진행하여, 각 조건의 분말이 가진 외형 및 결정 크기를 확인하였다. 제조한 세리아 입자의 1차 입자의 크기는 15 ~ 20 nm 의 크기를 가지고, 2차 입자는 200 nm 크기부터 수 μm까지로 크기가 다양함을 확인하였다. 제조한 슬러리의 물리적·화학적 분석인 pH, Conductivity, 입자 크기, 제타 전위를 측정하여 각 슬러리의 안정성 및 슬러리로서의 적합성을 확인하였다. 각 슬러리의 제거 효율을 측정하기 위해 MRR 테스트를 진행하였고, 제거율은 폴리싱 전후의 두께 차이를 통해 계산되었다. 또한 평탄도는 폴리싱 후의 두께 측정값들의 최소값 및 최대값을 통해 계산되었다. HA800 샘플의 경우, 제타 전위의 절댓값이 40 mV 로 유지되며 안정적인 거동을 보였으며, 제거율 및 비평탄도는 HDP 막질에서는 1018 Å, 4.08, NIT 막질에서는 302.3 Å, 3.89, Poly 233.5 Å, 2.07로, 높은 제거율과 함께 낮은 비평탄도, 높은 선택비를 가진다. 이를 통해 가장 CMP 공정에 적합한 슬러리는 Air 환경에서 800℃ 온도에서 소성한 HA800 샘플이 가장 적합함을 알 수 있다.
The chemical mechanical polishing/planarization (CMP) with the advancement of integrated circuit (IC) technology, processes are evolving to meet the technical requirements of fine line widths and the need for multi-layer wiring. This study reports the synthesis and systematic evaluation of ceria-based CMP slurries intended for interlayer dielectric (ILD) and shallow trench isolation (STI) processes. Ceria (CeO2) powders were prepared by calcining a cerium-carbonate precursor at 600-800 °C for 5 h, dispersed with a commercial dispersant (D), and processed via vertical milling to obtain aqueous colloidal slurries. Precursor decomposition was examined by thermogravimetric analysis (TGA). The morphology and crystallography of calcined powders were characterized by colorimetry, SEM/TEM, and XRD to estimate particle and crystallite sizes. The primary particles of the synthesized ceria were 15-20 nm in size, while the secondary particles were approximately 200 nm. Slurry physicochemical stability after milling was quantified via pH, conductivity, particle-size distribution, and zeta potential. Polishing performance was assessed by the material removal rate (MRR), computed from pre- and post-polish film thickness, and by planarity, obtained from the post-polish thickness range; common defect modes (ring, scratch, zone, repeat) served as qualitative criteria. The integrated synthesis-formulation-characterization workflow relates precursor calcination and dispersant-assisted dispersion to colloidal stability and wafer-level outcomes, providing a basis for optimizing CeO2 slurry formulations under stringent CMP requirements. The HA800 slurry showed an absolute zeta potential of about 40 mV, indicating a stable dispersion. Under this condition, the HDP, nitride, and polysilicon films exhibited removal rate/non-uniformity values of 1018 Å/4.08, 302.3 Å/3.89, and 233.5 Å/2.07, respectively, confirming high removal efficiency, low non-uniformity, and high selectivity, so HA800 (calcined at 800 °C in air) was identified as the most suitable slurry for CMP.
Keywords
CMP(Chemical Mechanical Polishing)
Calcined ceria
Calcined ceria
Slurry stability
Material Removal Rate(MRR)
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Information
  • Publisher :The Society of Convergence Knowledge
  • Publisher(Ko) :융복합지식학회
  • Journal Title :The Society of Convergence Knowledge Transactions
  • Journal Title(Ko) :융복합지식학회논문지
  • Volume : 13
  • No :4
  • Pages :109-124
  • DOI :https://doi.org/10.22716/sckt.2025.13.4.010
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