The removal of copper oxide using acetic acid at low temperatures was investigated. Acetic acid removes a variety of copper oxides, including cuprous oxide, cupric oxide, and cupric hydroxide without attacking the underlying copper film. The removal of these oxides was determined by X-ray photoelectron spectroscopy. Acetic acid can tolerate up to 4 vol % water dilution without hindering the oxide removal while producing an oxide-free surface. However, if a deionized water rinse is performed after an acetic acid treatment, a surface film of cupric hydroxide forms immediately. An acetic acid treatment at 35°C without a water rinse removes the native copper oxide and produces an oxide-free, streak-free copper surface.
Polymer film removal from silicon surfaces was investigated using acetic acid at low temperatures. The polymer materials studied included poly͑methyl methacrylate͒, poly͑4-hydroxystyrene͒, and commercial positive photoresist ͑Shipley 1813͒. All polymer films studied were removed by acetic acid at 35°C, apparently by dissolution and in some cases, lift-off from the polymer-silicon interface. If an adhesion-promoting layer such as hexamethyldisilazane was applied to the silicon surface prior to polymer application, a thin carbon-based residue remained on the silicon surface as detected by X-ray photoelectron spectroscopy. A proposed solubility removal mechanism was investigated by using propionic and trifluoroacetic acids, since these acids possess different solubility and reactivity properties than acetic acid. Acetic acid was the most efficient for polymer removal and was capable of removing B ϩ and P ϩ ion-implanted (10 12 atoms/cm 2 ) photoresist.
Articles you may be interested inFabrication of tapered graded-refractive-index micropillars using ion-implanted-photoresist as an etch maskThe ability of water and water/1% carbon dioxide mixtures to remove ion-implanted photoresist from silicon substrates was investigated. Photoresist with implant levels up to 2ϫ10 15 /cm 2 of boron and phosphorus were stripped effectively at a temperature of 165°C and a pressure of 58.6 bar ͑850 psi͒ by both water and water/carbon dioxide. Removal of photoresist at low implant levels (2 ϫ10 12 /cm 2 ) proceeded rapidly, while samples at higher dose levels (Ͼ2ϫ10 15 /cm 2 ) had a thin carbonized layer at the photoresist surface that inhibited the removal rate. Removal of this carbonized layer required approximately 2 min for water/carbon dioxide and approximately 8 min for water, while complete removal of the remaining photoresist film took less than 30 min for both fluids. Patterned, arsenic-implanted (1ϫ10 16 /cm 2 ) photoresist layers were removed by water/ carbon dioxide at 200°C, 850 psi, 3 ml/min flow rate, and 30 min exposure. Under all conditions investigated, water/carbon dioxide proved more effective than pure water at removing ion-implanted photoresist.
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