Technical-Report

Introduction of Aqua Plasma Boost® and AQ-2000BT:
Excellent for Reducing Large Sized Samples of Oxidized Copper
New Business Development Division, Samco, Inc.

Introduction
Samco focuses on product development with an emphasis on environment,
health and safety (EHS). We have been advancing research on water vapor
plasma at low pressure, Aqua Plasma® [1], and product development using thistreatment method. H, O, and OH radicals are generated in the plasma, andreduce oxidized copper or silver electrodes, remove organic residue, and makethe surface superhydrophilic. This method is widely used in semiconductor
back-end processes such as wire bonding and molding on lead frames.
Its applications have included reduction of electrodes, cleaning of organic
residues, and hydrophilization to improve wettability or adhesion. Nowadays,
the Aqua Plasma® has expanded to front-end processes such as descum
process to remove photoresist residue on the copper electrode prior to plating.
Moreover, the range of applications has expanded to include ø12˝ wafers.
However, it had an upper size limit for reducible oxidized copper.
This report introduces Aqua Plasma Boost® newly developed to reduce large
sized samples of oxidized copper and the system AQ-2000BT.
Aqua Plasma Boost® and AQ-2000BT
Reductionof oxide metals(Available to 12 inches)

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Aqua Plasma Boost® enhances its reduction performance by using reducing
gas in addition to water vapor (patent pending). It also has excellent organic
matter decomposition and hydrophilic effects as shown in Figure 1(a). Figure1(b) shows the appearance of AQ-2000BT connected to a booster. The reducing
gas is produced by the booster in the required quantities. The booster and thereducing gas are easy to handle and safe to use.
AQ-2000BT supports large diameter wafers and large size substrates withcopper electrodes. In addition, production batch and magazine processing arealso available (Figure 2).

n(a) Effects of Aqua Plasma Boost®

Wafer process

Batch process

Magazine process※※ It need the frame space 6mm or more. Applicability depends on the purpose.

Figure 2. Available sample set types of Aqua Plasma Boost®

Booster(b) AQ-2000BT
Figure 1. Aqua Plasma Boost® and AQ-2000BT

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Technical-Report
Reduction Performance
Reduction performance of Aqua Plasma Boost® was evaluated using a ø12˝copper plate oxidized to a depth of 40 nm. A previous study [2] reports thatthe copper color changes with the thickness of the oxide film and oxidized
copper can be reduced to a depth of about 200 nm based on XPS analysis andSEM cross-sectional observations. Because the copper oxide layer is thinnerthan 200 nm, it is considered possible to determine whether the reduction isappropriate or not based on the color change.
Aqua Plasma® could not reduce the oxidized ø12˝ copper plate, whereas
Aqua Plasma Boost® completely reduce it(Figure 3). The reduction time was
3 minutes.

Before treatment

After treatment

Aqua Plasma®

Aqua Plasma Boost®
Figure 3. Appearance changeof oxidized ø12˝
copper plates

Decomposition and Superhydrophilization
Aqua Plasma Boost® can decompose photoresist or organic residue on
copper surface simultaneously in the reduction process. During the 3 minutes
process, approximately 30nm of photoresist is expected to be removed.
This amount satisfies typical requirements for post-process cleaning anddescum processes. In addition, many types of photoresist surface aresuperhydrophilized with contact angles below 10°. Therefore, this method is
also expected to improve adhesiveness of mold resin and wettability of platingsolutions.
Postscript
AQ-2000BT has a more detailed introduction and demonstration system.
Wafer transfer type can also be manufactured. Feel free to contact us if you
have any questions.

References[1] SAMCO NOW Vol. 94, 96, 100, 102, 107, and111[2] H. Terai, et al. Reduction of Copper Oxide by
Water Vapor Plasma at Low Pressure IEEJ
Trans. Sensors Micromachines 139, 157-162(2019). 11-14, 2019.

Samco Inc.
For more information please email: info@samco.co.jp
vol.121 / 2023. APR.

URL: https://www.samco.co.jp/en/2