Press Releases


December 7, 2010

Promoting the Use of "Green Sulfaceed KD™" as a System Proven to Enable Ashing-less Photoresist Removal in Semiconductor Manufacturing

Kurita Water Industries, Ltd. (headquarters: Shinjuku-ku, Tokyo; President: Hiroshi Saito) is promoting the use of its electrolyzed sulfuric acid generator "Green Sulfaceed KD™" in semiconductor manufacturing as a system proven to enable stable resist removal without any prior need for ashing.

The resist removal process traditionally uses a mixed solution of sulfuric acid and hydrogen peroxide (SPM). In the SPM process, the resist removal performance of the solution gradually deteriorates as it is used over a length of time; therefore, prior plasma ashing (ashing) is generally necessary. Ashing is a dry process in which resist is ashed at a high temperature. However, by applying "Green Sulfaceed KD™", which has a high resist removal performance, the ashing process can be omitted and resist can be removed through the wet cleaning process alone. In addition, as "Green Sulfaceed KD™" eliminates the need for the SPM process, the use of chemicals is significantly reduced.

Since Kurita delivered its first "Green Sulfaceed KD™" to a leading U.S. semiconductor manufacturer, it has received multiple orders for the system. Kurita will further promote sales of this system to semiconductor manufacturers both within Japan and overseas to spread ashing-less resist removal in semiconductor manufacturing and thereby help customers improve their productivity and reduce their environmental impact.

  • *Photoresist is a resin used in the formation of semiconductor circuits, which is removed after the circuits are formed.

1. Outline of "Green Sulfaceed KD™"

External view of the system (for resist removal on 100 to 250 300-millimeter wafers per hour)

External view of the system
(for resist removal on 100 to 250
300-millimeter wafers per hour)

"Green Sulfaceed KD™" is a system to electrolyze sulfuric acid to generate peroxosulfuric acid, which has an extremely high oxidizing power, for use in the resist removal process in semiconductor manufacturing. The resulting enhanced sulfuric acid is transferred to the cleaning machine, where the resist on wafers is removed. Because the used sulfuric acid can be recycled, liquid waste volume can be significantly reduced. Compared with the conventional SPM processing, this new system allows semiconductor manufacturers to remove resist with the same or higher performance while reducing the use of chemicals. Moreover, sulfuric acid is continually electrolyzed and this allows semiconductor manufacturers to maintain a constant concentration of peroxosulfuric acid to ensure a consistent resist removal effect over many hours, stabilizing the process.

2. Actual Performance of "Green Sulfaceed KD™"

Kurita confirmed that the resist removal performance of "Green Sulfaceed KD™" for wet batch systems was on the same level or higher compared with the performance of the traditional SPM method in trial uses of the system by semiconductor manufacturers both within and outside Japan. The system is also proved to enable ashing-less resist removal. Specifically, "Green Sulfaceed KD™" was used by Renesas Electornics in Japan in its manufacturing process for general-use semiconductors and by a leading U.S. semiconductor manufacturer in its state-of-the-art semiconductor manufacturing process. In both of these cases, the use of the system obviated the need for prior ashing. Based on the results, Kurita expects that application of the system would help semiconductor manufacturers shorten the time taken by their resist removal process by up to half compared with the conventional process.

In cooperation with Kurita, Renesas Electronics presented the results at the meeting of the Japan Society of Applied Physics held in September. The leading U.S. semiconductor manufacturer also made a presentation—again with Kurita—at the International SEMATECH Manufacturing Initiative (ISMI) 2010 held in November.

  • *Ion implant doses in the resist surface in the cases where the effect of "Green Sulfaceed KD™" was proved:
    Leading U.S. semiconductor manufacturer: 1×1015atoms/cm2
    Renesas Electronics: 5 ×1014atoms/cm2

3. Future Development

In recent years, semiconductor manufacturers have been continuously improving their manufacturing processes not only for microfabrication, but also for increasing productivity, reducing cost, and minimizing environmental impact. In addition, in the resist removal process, demand for removal without prior ashing as well as for a reduction in the use of chemicals is increasing. The market for "Green Sulfaceed KD™", therefore, is expected to significantly expand in the future.

Kurita will promote sales of this system to semiconductor manufacturers worldwide. The Company will also work to foster the use of the system in the leading-edge single wafer cleaning process. Through these measures, Kurita will contribute to the spread of ashing-less resist removal in semiconductor manufacturing and help its customers solve their problems.