Shallow defect layer formation as Cu gettering layer of ultra-thin Si chips using moderate-pressure (3.3 kPa) hydrogen plasma

Abstract

In this study, we developed a shallow defect layer formation process using moderate-pressure H2 plasma at 3.3 kPa for an extrinsic gettering layer of ultra-thin Si chips aimed at three-dimensional integrated circuits. This process can be conducted in the presence of trivial amounts of air impurities (∼0.01 vol. %), thereby avoiding the use of high-vacuum equipment. We investigated the dependence of defect formation behavior on various processing parameters such as H2 flow rate, processing time, substrate temperature, and input power. It was determined that the absence of H2 gas flow was favorable for the defect layer formation because Si etching by hydrogen atoms was suppressed. A low Si temperature and high input power are desirable for a high defect density in the shallow surface region of the extrinsic gettering layer. When pulse-modulated plasma irradiation was attempted, the defect layer that formed became thinner and had a higher defect density than that obtained by continuous plasma, demonstrating good Cu gettering performance. Without using harmless chemicals, or high-cost equipment, a shallow gettering layer can be formed using inexpensive H2 gas.