Study On The Surface Layer Damage Of Monocrystalline Silicon Wafer Induced By Ultra-precision Grinding

Monocrystalline silicon wafers are the most widely used substrates in IC manufacturing fields. The surface layer quality directly affects the property, the rate of finished products and the lifetime of IC device. With the increasing of the wafer diameter, some new processes for wafer machining are being researched. Wafer rotation grinding, as a precision grinding method, is widely used in manufacturing and back thinning process of silicon wafer due to its low damage, high precision and efficiency. However, grinding would inevitably bring about surface layer damage and the damage will severely affect the process time of the subsequent polishing procedure. Although many researchers study the machined wafer damage, the damage mechanism of the wafer rotational grinding is not yet perfectly understood. Therefore, the research regarding the surface layer damage in wafer rotation grinding has an important significance for realizing process of the wafer with high efficiency, precision, undamaged and ultra-smooth surface.Based on adequate analysis of research background, the rotation ground wafer surface layer damage is studied in this paper. The main research work is listed as follows:(1) Base on different damage forms, the wafer surface layer damage measurement methods are analyzed. Damage measurement methods and the implementation schemes are determined by doing abundant experiments.(2) The change rules and the generation reasons of wafer damage microstructure induced in rough, semi-fine and fine grinding are studied by using TEM and Raman microspectroscopy. The surface layer microcrack configuarations and distribution of single diamond grit ground and diamond wheel ground wafer are also studied. The phase transformation of the monocrystalline silicon during grinding is analyzed as well.(3) The residual stress distributions of single diamond grit ground and diamond wheel ground wafer surface layer are studied. The generation reasons of residual stress are analyzed.(4) The subsurface damage depths (SSD) of different positions on the rotation ground wafer surface are detected and analyzed. The damage distribution rules and the effects of the grinding parameters on the SSD are studied.The following conclusions are obtained by systematical experimental study and theoretical analysis:(1) Rough ground wafer surface layer damage is composed of large quantity of microcracks with complicated configuarations, high density dislocations, stalk faults and elastic deformation layer. Among them microcracks, dislocations and stalk faults are dominant. The SSD is 8~ 17 μm. Apart from the above damage forms, amorphous layer and polycrystalline layer exist in the semi-fine and fine ground wafer surface layer damage, and...