Specific Process Knowledge/Thin film deposition/Electroplating-Ni: Difference between revisions
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[[image:choi_2017_Machine_overview.jpg|200x200px|right|thumb|Electroplating-Ni positioned in cleanroom A-1]] | [[image:choi_2017_Machine_overview.jpg|200x200px|right|thumb|Electroplating-Ni positioned in cleanroom A-1]] | ||
The Technotrans microform.200 (Electroplating-Ni in LabManager) is a machine capable of depositing nickel electrochemically. This is done by lowering the sample into an electrolyte containing nickel ions and then apply a voltage across the sample and the anode. The anode is a basket filled with nickel pellets. The cathode is the sample to be coated with nickel. | The Technotrans microform.200 (Electroplating-Ni in LabManager) is a machine capable of depositing nickel electrochemically. This is done by lowering the sample into an electrolyte containing nickel ions and then apply a voltage across the sample and the anode. The anode is a titanium basket filled with nickel pellets. The cathode is the sample to be coated with nickel. | ||
At the anode metallic nickel is oxidized to nickel ions: | At the anode metallic nickel is oxidized to nickel ions: | ||
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The minimal charge accepted by the software on the machine is 0.1 Ah (Ampere-hours). This corresponds to roughly 2 µm of nickel on a four inch wafer. You can abort a program prematurely to achieve even lower thicknesses, but this requires manual control of the machine. | The minimal charge accepted by the software on the machine is 0.1 Ah (Ampere-hours). This corresponds to roughly 2 µm of nickel on a four inch wafer. You can abort a program prematurely to achieve even lower thicknesses, but this requires manual control of the machine. | ||
The maximum allowed thickness is ~1,4 mm (1400 µm), since a higher thickness will make the release of the sample difficult and likely damage the sample holder. This corresponds to a charge of 53-54 Ah on a four inch wafer. | The maximum allowed thickness is ~1,4 mm (1400 µm), since a higher thickness will make the release of the sample difficult and likely damage the sample holder. This corresponds to a charge of 53-54 Ah on a four inch wafer. Please contact Danchip before processing your wafer if you intend to deposit more than ~500 µm of nickel, since this can involve special challenges regarding uniformity, roughness and sample release after plating. | ||
The plating bath is an aqueous solution of nickel sulfamate, boric acid and sulfamic acid. The bath is moderately acidic (pH = 3, | The plating bath is an aqueous solution of nickel sulfamate, boric acid and sulfamic acid. The bath is moderately acidic (pH = 3,70). The pH is kept constant by an automatic pH measurement and sulfamic acid dosing module. The temperature of the bath is 52°C. The sample will spin at 60 RPM during deposition. | ||
Uniformity across a 4" wafer is around 5% for the standard processes (the edge being slightly thicker than the center of the sample). Running at high current densities will deposit a nickel layer that is quite soft. Decreasing current density will increase tensile strength of the deposited nickel. | Uniformity across a 4" wafer is around 5% for the standard processes (the edge being slightly thicker than the center of the sample). Running at high current densities will deposit a nickel layer that is quite soft. Decreasing current density will increase tensile strength of the deposited nickel. | ||