Full-Sized Panel Photodesmear for Via Residue Cleaning

Recently, it is required that the high density interconnect substrates implemented to the electrically functional devices must be smaller and thinner because of the rapid spread of IoT. Microelectronics assembly and packaging technology also require higher density wiring and packaging. We have developed a new desmear technology applied with ultraviolet rays (named Photodesmear technology). We reported that this Photodesmear technology is a new fundamental technology for the next generation packaging technology that requires the high density wiring and fine patterning. In addition, it is the environmentally friendly technology without adopting any harmful chemicals. Photodesmear is a smear removal process which consists of irradiation processing of ultra violet rays and flush processing. We conducted evaluation the basic value by the coupon level in 2013 and announced the validity of Photodesmear. Various problems were cleared in the Photodesmear process of micro via, and got the following result which leads to practical use, so then the following items will be reported: 1). We built a tool for panels and succeeded in proof of Photodesmear in a full-sized panel. A newly developed lamp was adopted into the tool and achieved batch processing in whole full sized area. 2). We confirmed the smear removal uniformity in the micro via bottom in a full-sized panel. 3). We made dry seed layer formation and electrolysis plating process after Photodesmear processing. And we confirmed the high peel strength(0.7 kgf/cm) and via connectivity. 4). We considered a mechanism of a smear removal process by irradiation processing of ultraviolet rays. Feasibility of Photodesmear has been found by equipment development and process development. A dry process by Photodesmear can respond positively to the request of marketing regarding future high density wiring and fine patterning.