Effects of pH on photochemical decomposition of perfluorooctanoic acid in different atmospheres by 185nm vacuum ultraviolet

The desmear process of removing via residue after laser drill in substrate manufacturing is a critical step for reliability and electrical performance. Cost effective and environmentally clean desmear processes are industry-wide objectives, as the current wet desmear process results in significant chemical waste and regular bath replacement. Here, we evaluated an effective photo desmear method targeting a low total cost of ownership and negligible environmental impact. This method achieves residue and silica free via bottoms with the use of 172nm vacuum ultraviolet light (VUV) photo-chemical ashing followed by water clean. Studies of organic molecular photochemical decomposition by short wavelength UV light are widely reported and have been applied for purposes such as surface cleaning and improving wettability and are naturally extendable to via residue removal. Scanning electron microscope (SEM) and energy dispersed X-ray spectroscopy (EDX) reveal that the application of VUV desmear results in residue free microvia without negatively affecting via shape or the dielectric surface. In addition, the surface remains highly wettable, which aids downstream copper plating. The high reaction rate, absence of wet chemistry, and creation of surfaces amenable for subsequent copper plating make this dry desmear process a strong candidate for future applications in substrate manufacturing.

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Photodegradation of perfluorooctanoic acid by 185 nm vacuum ultraviolet light

Journal of Environmental Sciences ◽

10.1016/s1001-0742(07)60064-3 ◽

2007 ◽

Vol 19 (4) ◽

pp. 387-390 ◽

Cited By ~ 71

Author(s):

Jing CHEN ◽

Peng-yi ZHANG ◽

Jian LIU

Keyword(s):

Ultraviolet Light ◽

Vacuum Ultraviolet ◽

Perfluorooctanoic Acid

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The defluorination of perfluorooctanoic acid by different vacuum ultraviolet systems in the solution

Water Environment Research ◽

10.1002/wer.1448 ◽

2020 ◽

Author(s):

Yuanhao Li ◽

Qiufeng Lin ◽

Cong Li ◽

Zijian Weiguo ◽

Luo Xu ◽

...

Keyword(s):

Vacuum Ultraviolet ◽

Perfluorooctanoic Acid

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Effects of pH and coexisting chemicals on photolysis of perfluorooctane sulfonate using an excited xenon dimer lamp

Water Science & Technology ◽

10.2166/wst.2017.526 ◽

2017 ◽

Vol 77 (1) ◽

pp. 108-113 ◽

Cited By ~ 1

Author(s):

Naoyuki Kishimoto ◽

Koji Doda

Keyword(s):

Degradation Rate ◽

Vacuum Ultraviolet ◽

Removal Rate ◽

Perfluorooctane Sulfonate ◽

Sulfate Solution ◽

Inorganic Materials ◽

Sulfate Ions ◽

Uv Photolysis ◽

Vuv Photolysis ◽

Effects Of Ph

Abstract Vacuum ultraviolet (VUV) photolysis at the wavelength of 172 nm in a sulfate solution was introduced as a more efficient process for perfluorooctane sulfonate (PFOS) degradation than ultraviolet (UV) photolysis at 254 nm. The effects of pH and coexisting chemicals on VUV photolysis under the coexistence of 100 mM sulfate were investigated. VUV irradiation successfully degraded PFOS, and the degradation rate was 5.5 times higher than by UV photolysis. Direct VUV photolysis was inferred to mainly contribute to PFOS degradation. PFOS degradation by VUV irradiation was enhanced at pH less than 2 due to sulfate radicals generated via VUV photolysis of sulfate ions. Consequently, VUV photolysis was superior to UV photolysis for PFOS removal on both the removal rate and energy efficiency. However, the inorganic chemicals phosphoric acid and nitric acid strongly inhibited PFOS degradation, probably by masking PFOS from VUV rays by their VUV absorption. Accordingly, PFOS separation from inorganic materials such as phosphate and nitrate will be recommended for the application of VUV techniques for PFOS removal. In this research, organic solvent abstraction was inferred to be one of candidates for PFOS separation.

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Photochemical decomposition of perfluorooctanoic acid in aqueous periodate with VUV and UV light irradiation

Journal of Hazardous Materials ◽

10.1016/j.jhazmat.2010.02.030 ◽

2010 ◽

Vol 179 (1-3) ◽

pp. 1143-1146 ◽

Cited By ~ 63

Author(s):

M.H. Cao ◽

B.B. Wang ◽

H.S. Yu ◽

L.L. Wang ◽

S.H. Yuan ◽

...

Keyword(s):

Uv Light ◽

Perfluorooctanoic Acid ◽

Light Irradiation ◽

Uv Light Irradiation ◽

Photochemical Decomposition

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Photochemical decomposition of perfluorooctane sulfonate (PFOS) in an anoxic alkaline solution by 185nm vacuum ultraviolet

Chemical Engineering Journal ◽

10.1016/j.cej.2015.06.022 ◽

2015 ◽

Vol 280 ◽

pp. 241-247 ◽

Cited By ~ 25

Author(s):

Ling Jin ◽

Pengyi Zhang

Keyword(s):

Alkaline Solution ◽

Vacuum Ultraviolet ◽

Perfluorooctane Sulfonate ◽

Photochemical Decomposition

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Efficacy of vacuum ultraviolet photolysis for bromate and chlorate removal

Water Science & Technology Water Supply ◽

10.2166/ws.2015.039 ◽

2015 ◽

Vol 15 (4) ◽

pp. 810-816

Author(s):

Naoyuki Kishimoto ◽

Yumeko Yamamoto ◽

Syou Nishimura

Keyword(s):

Energy Efficient ◽

Vacuum Ultraviolet ◽

Tap Water ◽

Pure Water ◽

High Concentration ◽

Uv Photolysis ◽

Bicarbonate Ions ◽

Vuv Photolysis ◽

Effects Of Ph ◽

Ultraviolet Photolysis

We introduce vacuum ultraviolet (VUV) photolysis at 172 nm as a more efficient process for bromate and chlorate removal than conventional ultraviolet (UV) photolysis at 254 nm. We discuss the effects of pH and coexisting salts on VUV photolysis. In experiments at various pH levels, the VUV photolysis performance decreased in the alkaline region for pH above 7. Furthermore, nitrate and inorganic carbon compromised the performance, probably owing to the generation of active oxidant species (such as hydroxyl radicals and carbonate radicals) during the photolysis. However, photochemical experiments conducted in pure water revealed that VUV photolysis is 4.1-fold more energy efficient than UV photolysis using a low-pressure mercury lamp. Although the performance of VUV photolysis in tap water was about 40% less efficient than that in pure water, mainly owing to the presence of bicarbonate ions, the performance was still higher than that of UV photolysis in pure water. However, VUV photolysis may not be feasible in tap water with a high concentration of nitrate ions, because nitrate produces a stronger inhibition effect than other salts.

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