Damascene 구조를 갖는 반도체소자의 구리금속배선 식각공정에서 배선재료에 의해서 발생되는 구리 식각잔류물을 제거하기 위해 oxalic acid (OA), lactic acid (LA) 및 citric acid (CA)의 카르복시산 함유된 반수계 혼합세정액을 제조하고 특성을 분석하였다. 카르복시산은 pH에 따라 카르복실기와 구리이온들과의 다양한 복합체를 형성하며 세정특성의 변화를 준다. 카르복시산들이 함유된 각각의 세정액의 세정특성평가결과 10 wt% CA를 함유한 반수계 세정액의 식각잔류물 세정특성은 pH 2에서 7까지의 영역에서 가장 낮은 구리 식각률을 보였으며 pH 2에서 4까지 구리에 대한 구리산화물의 가장 높은 식각 선택도를 나타내었으나 pH 5에서 7 범위에서는 10 wt% LA가 함유된 세정액이 더 높은 선택도를 보였다. 따라서 표면세정효과는 pH에 따라 변화하며 적절한 카르복시산을 사용함이 요구된다. CA가 함유된 세정액의 경우에 CA 농도와 구리에 대한 구리산화물의 식각 선택도의 증가특성을 보이며 CA가 5 wt%이상 함유된 경우에는 세정 후 구리배선의 표면이 88 %이상의 금속구리로 분석되어 구리산화물로 구성된 식각 잔류물의 제거에 효과적임을 알 수 있었다.

In this study, semi-aqueous solutions containing carboxylic acids such as oxalic acid (OA), lactic acid (LA) and citric acid (CA) were formulated for the removal of copper etching residues produced at the interconnection process, and their characteristics were analyzed. Carboxylic acids in the solutions were apt to form various copper complexes according to the value of pH. Semi-aqueous solution containing 10 wt% CA showed the lowest etching rate of copper in the range from pH2 to pH7 and the highest selectivity in the range of pH 2 to pH 4. However, the cleaning solution containing 10 wt% LA revealed the superior selectivity at the range from pH 5 to pH 7. Appropriate selection of carboxylic acid should be required to improve the performance of cleaning solution. In the case of CA, the etching selectivity of copper oxide complex to copper was increased with the concentration of CA in the solution, when the solutions contain over 5 wt% CA, the copper interconnection layer has a metallic copper surface more than 88% in the area. The result shows that CA contained semi-aqueous solution has a relatively good cleaning ability.

Post-etch residue Etch rate Selectivity Copper oxides Citric acid

Kitajima H, Shiramizu Y, IEEE Trans. Semicond. Manuf., 10, 267 (1997)
Engelhardt M, Schindler G, Steinhogel W, Steinlesberger G, Microelectron. Eng., 64, 3 (2002)
Lee SW, Kim JJ, Korean Chem. Eng. Res., 53(4), 517 (2015)
Tan YS, Thin Solid Films, 462-463, 250 (2004)
Abe H, Yoneda M, Fujiwara N, Jpn. J. Appl. Phys., 47, 1435 (2008)
Hussein M, He J, IEEE Trans. Semicond. Manuf., 18, 69 (2005)
Reinhardt KA, Kern W, “Handbook of Silicon Wafer Cleaning Technology,” 2nd ed., 208-210, William Andrew, NY, USA (2008).
Johansson I, Somasundaran P, “Handbook for Cleaning/Decontamination of Surfaces,” 1st ed., 459-483, Elsevier, Amsterdam, NED(2007).
Venkataraman N, Raghavan S, Microelectron. Eng., 87, 1689 (2010)
Moore JC, “Successful Photoresist Removal: Incorporating Chemistry, Conditions, and Equipment,” Proceedings SPIE 4690 Advances in Resist Technology and Processing XIX. March 3, Santa Clara, USA(2002).
Venkataraman N, Muthukumaran A, Raghavan S, “Evaluation of Copper Oxide to Copper Selectivity of Chemical Systems for BEOL Cleaning Through Electrochemical Investigations,” 2007 Materials Research Society proceedings. April 9-13, San Francisco, USA(2007).
Macdougall J, Reid C, McGhee L, Solid State Phenom., 134, 329 (2008)
Roberge PR, “Handbook of Corrosion Engineering,” 1st ed., 500-502, McGraw-Hill, NY, USA(2000).
Ko CK, Lee WG, Surf. Interface Anal., 44, 94 (2012)
Gorantla VRK, Babel A, Pandija S, Babua SV, Electrochem. Solid State Lett., 8(5), G131 (2005)
Gorantla VRK, Goia D, Matijevic E, Babu SV, J. Electrochem. Soc., 152(12), G912 (2005)
Patri UB, Aksu S, Babu SV, J. Electrochem. Soc., 153(7), G650 (2006)
Ko CK, Lee WG, Surf. Interface Anal., 42, 1128 (2010)
DeNardis D, Rosales-Yeomans D, Borucki L, Philipossian A, Thin Solid Films, 513(1-2), 311 (2006)
Apen E, Rogers BR, Sellers JA, J. Vac. Sci. Technol. A, 16(3), 1227 (1998)
Wagner CD, Muilenberg GE, “Handbook of X-ray Photoelectron Spectroscopy,” 10th ed., 86-87, Perkin Elmer, MN, USA (1992).
Ko CK, Lee WG, J. Korean Ind. Eng. Chem., 19(2), 236 (2008)
Suzuki T, Otake A, Aoki T, Solid State Phenom., 145-146, 315 (2009)