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

In this study, we developed a shallow defect layer formation process using moderate-pressure H-2 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 (similar to 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 H-2 flow rate, processing time, substrate temperature, and input power. It was determined that the absence of H-2 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 H-2 gas.