Papers by Keyword: Single Silicon Wafer

Abstract: The ice fixed abrasives (IFA) polishing is a potential polishing process in the semiconductor industry to realize superior surface finish and planarity for semiconductor wafers. The key question in IFA polishing is how to keep suitable ambient temperature and melting rate in production process in order to avoid premature failure of the IFA pad. In this paper, effects of ambient temperature (T), pressure in cylinder (Pc), rotary speed of IFA pad (v) and eccentricity of pressure head (e) on temperature distribution and melting rate of the IFA pad are researched. The results show that T should be kept at about 10 °C in order to control the melting rate of the IFA pad effectively and keep longer polishing time. And suitable Pc, e can be kept at 0.075 MPa or 0.1 MPa and 20 mm or 30 mm, respectively. In order to increase IFA polishing efficiency, the rotary speed of IFA pad can be increased appropriately. All the results provide the basis for choosing suitable processing parameters in IFA polishing.

Abstract: The key question in the ice fixed abrasives (IFA) polishing is how to keep suitable ambient temperature in production process in order to avoid premature failure of the IFA. Based on above, the three dimensions finite element analysis (FEA) model of IFA polishing temperature field is built up at first. Then, the model reliability is demonstrated by experiments. Effects of ambient temperature and polishing time on temperature distribution and melting rate of the IFA pad are researched. The results show that the ambient temperature should be kept at about 10 °C in order to control the melting rate of the IFA pad effectively and keep longer polishing time. All the results provide the basis for choosing suitable ambient temperature in polishing.

Abstract: Ice fixed abrasives (IFA) polishing is a novel ultra-precision machining method. The motion tracks of abrasives during IFA polishing have an important effect on the quality of the machined silicon wafer. Firstly, the motion tracks of IFA polishing are theoretically analyzed in this paper. It is founded that the paths of any point in the IFA polishing pad relative to the wokpiece are a group of cycloids. Then, the motion tracks of single abrasive and multiple abrasives in the IFA polishing pad are simulated respectively. The results show that increasing the eccentricity is beneficial to the enlargement of the size range of polishing process. With the increasing of the speed ratio between the IFA polishing pad and the workpiece, the abrasive at higher speed can leave longer tracks on the workpiece than that at lower speed at the same time. The more the abrasives, the more uniform the mark density under the influence of more abrasives.

Abstract: The friction behavior of single silicon wafer sliding against different ice counterparts (α-Al2O3, CeO2 and SiO2) at 10±0.5 °C within a velocity of 60 rpm~300 rpm were studied using a home-made friction and wear testing machine. The morphologies and surfaces roughness of the worn silicon wafers were observed and examined on a non-contact surface topography instrument (ADE). It was found that the friction coefficient of the single silicon wafer decreased with the increase of sliding velocity. Single crystal silicon wafer coupled with α-Al2O3 ice counterpart recorded the highest friction coefficient and the biggest surface roughness, while it had the lowest friction coefficient and the smallest surface roughness as with CeO2 ice counterpart. One reason was that a series of tribochemical reactions occurred at the local contact point between the ice counterpart and the silicon wafer during sliding. Under alkaline condition, there would be a soft corrosion layer formed on the surface of the silicon wafer. Another reason was that the hardness of the abrasive particles was different and this caused different cutting depth of them.

Abstract: Hardness, elastic modulus and scratch resistance of single silicon wafer are measured by nanoindentation and nanoscratching using a nanoindenter. Fracture toughness is measured by indentation using a Vickers indenter. The results show that the hardness and elastic modulus at a peak indentation depth of 100 nm are 12.6 and 166.5 GPa respectively. These values reflect the properties of the silicon wafer, the bulk material. The fracture toughness value of the silicon wafer is 0.74 Mpa·m1/2. The material removal mechanisms are seen to be directly related to the normal force on the tip. The critical load and scratch depth estimated from the scratch depth profile after the scratching and the friction profile are 138.64 mN and 54.63 nm respectively. If the load and scratch depth are under the critical values, the silicon wafer will undergo plastic flow rather than fracture. The critical scratch depth is different from that calculated from the formula of critical-depth-of-cut described by Bifnao et al and some reasons are given.

Abstract: Formation, propagation and length of crack and hardness of single silicon wafer were investigated at different temperatures by means of Vickers indentation, using lower temperature testing unit with semiconductor refrigerating chip and higher temperature testing unit with closed electric furnace. The results show that the hardness of single silicon wafer decreases with the increase of temperature, while the length of crack increases with the increase of temperature. Ductile-brittle transition of the single silicon wafer can occur at different temperatures with the increase of load. When the load is smaller and temperature is lower, no cracks can be found.

Abstract: Cryogenic polishing single silicon wafer with nano-sized CeO2 abrasives can be known as cryogenic fixed abrasives CMP (CFA-CMP). The abrasive slurry was made of nano-sized CeO2 particles dispersed in de-ionized water with a surfactant and the polishing slurry froze to form cryogenic polishing pad. Then the polishing tests of the blanket silicon wafers in the presence of the cryogenic polishing pad containing the nano-particulates were carried out. The morphologies and surfaces roughness of the polished silicon wafers were observed and examined on an atomic force microscope (AFM). The results show that a super smooth surface with roughness of 0. 293 nm is obtained within 5000 nm× 5000 nm and the removal of material is dominated by plastic flowage.