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Lecture 9 Through Mask Plating

Lecture 9 Through Mask Plating. 柳 克 強 x 4324 kcleou@ess.nthu.edu.tw. References: Madou, M., “ Fundamentals of Microfabrication”, CRC Press, 1998. Electro-deposition for Micro-devices. Through Mask Plating. Damascene Plating. Insulator deposition and patterning Seed-layer deposition.

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Lecture 9 Through Mask Plating

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  1. Lecture 9 Through Mask Plating 柳 克 強 x 4324 kcleou@ess.nthu.edu.tw References: Madou, M., “ Fundamentals of Microfabrication”, CRC Press, 1998.

  2. Electro-deposition for Micro-devices Through Mask Plating Damascene Plating Insulator deposition and patterning Seed-layer deposition Seed layer deposition and Patterning seed layer substrate Plating Plating Mask removal Seed-layer etching Planarization

  3. Electroplating Reactions: e- Ni2+ + 2 e- Ni (cathode reaction) 2Cl- 2 e- + Cl2 (anode reaction) anode cathode NiCl2 Ni + Cl2 2H+ + 2 e- H2 (competing reaction at cathode ) => PH value important !! KCl NiCl2 Na2+ Cl+ Amount of deposited material : KCl : Supporting electrolyte NiCl2 : Electro-active species F: Faraday constant (electricity required to deposit 1 g equivalent of substance) I : current t : deposition time M : molecular weigh of the depositing material z : ion’s charges #

  4. Diffusion Limited Reactions Diffusion limited cathode current: current density Nonlinear diffusion effect on microelectrodes

  5. Nonlinear diffusion effect on microelectrodes Effect of current density on stress

  6. 電 鍍 鎳(NTHU ESS Micro-fabrication lab) 電 鍍 結 果 配 方 • 氨基磺酸鎳 300 公克/公升 • 氯化鎳 20 公克/公升 • 硼酸 40 公克/公升 • LN-MU (應力降低劑) • LN-MA (平滑劑, 光澤劑) • 針孔抑制劑

  7. 電 流 密 度 影 響 • 電流密度 15 mA/cm2 • 電流密度 40 mA/cm2 其他參數：PH 值、溫度、表面活化劑

  8. High Aspect Ratio Structure Plating Challenges: Ni2+ current diffusion limited => deposition rate  H+ at bottom depleted => PH increase locally => form nickel hydroxide => deposition stopped

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