Papers by Author: Zhu Ji Jin

Abstract: Invar 36 alloy is widely used in the field of precision manufacturing owing to its minimal thermal expansion coefficient. Grinding is very important in Invar surface processing, and the thermal characteristics is a key factor to affect the residual stress and deformation of grinding. In this paper, the thermal characteristics of Invar 36 alloy during plane grinding was tested. The thermal characteristics of Invar 36 alloy was found to be between carbon steel and nickel-based superalloy. The lower grinding temperature and better ground surface with lower residual stress can be obtained by using the reasonable grinding parameters.

Abstract: With the development of IC manufacturing technology, the machining precision and surface quality of silicon wafer are proposed much higher, but now the planarization techniques of silicon wafer using free abrasive and bonded abrasive have the disadvantage of poor profile accuracy, environmental pollution, deep damage layer, etc. A soft abrasive wheel combining chemical and medical effect was developed in this paper, it could get super smooth, low damage wafer surface by utilizing mechanical friction of abrasives and chemical reaction among abrasives, additives, silicon. A comparison experiment between #3000 soft abrasive wheel and #3000 diamond abrasive wheel was given to study on the grinding performance of soft abrasive wheel. The results showed that: wafer surface roughness ground by soft abrasive wheel was sub-nanometer and its sub-surface damage was only 0.01µm amorphous layer, which were much better than silicon wafer ground by diamond abrasive wheel, but material removal rate and grinding ratio of soft abrasive wheel were lower than diamond wheel. The wafer surface ground by soft abrasive wheel included Ce4+, Ce3+, Si4+, Ca2+ and Si, which indicated that the chemical reaction really occurred during grinding process.

Abstract: In the process of CMP SiO2 ILD, the nano-particle with high surface energy in slurry has an essential impact on the efficiency and quality of CMP. In this paper the mode of nano-particle on the surface of SiO2 ILD is analysed and adhesion removal model corresponding to that is established. Through cycle polishing experiments, the change of nano-particle size and the state of particle surface before and after polishing is observed with TEM and Zeta potential analyzer, based on which the adhesion removal model is verified.

Abstract: This paper investigates two kinds of grinding wheels prepared by the combination of mechanical alloy and hot-press sintering (MA-HPS). Scanning electro microscopy, Optical microscope, Talysurf surface profiler, X-Ray diffraction and Raman spectroscopy were used to characterize two kinds of grinding wheels and identify the removal mechanism. It was found that FeNiCr matrix-TiC (FMT) grinding wheel yielded higher removal rate than TiAl abrasiveless carbophile (TAC) grinding wheel, which conversely owned good polishing quality; diamond was removed by transformation diamond to non-diamond carbons and then removed by mechanically or diffusion to grinding wheel during polishing process with FMT grinding wheel. While TAC grinding wheel polishing CVD diamond film mainly depended on the reaction between diamond carbon and titanium.

Abstract: A 3D profiler based on scanning white light interferometry with a lateral sampling interval of 0.11μm was introduced to measure the surface topography of a #3000 diamond grinding wheel, and a large sampling area could be achieved by its stitching capability without compromising its lateral or vertical resolution. The protrusion height distribution of diamond grains and the static effective grain density of the grinding wheel were derived, and the wheel chatter and the deformation of the wheel were analyzed as well. The study shows that the grain protrusion height obeys an approximate normal distribution, the static effective grain density is much lower than the theoretical density, and only a small number of diamond grains are effective in the grinding process with fine diamond grinding wheel. There exists waviness on the grinding wheel surface parallel with the wheel cutting direction. The cutting surface of the grinding wheel is not flat but umbilicate, which indicates that the elastic deformation at the wheel edges is much larger than in the center region.

Abstract: Invar 36 alloy is widely used in manufacturing instruments because of its minimal thermal expansion coefficient. As an important material for the components of precision or super-precision instruments, the process methods for Invar and the structure stability after its machining is necessary. In this paper, the residual stresses of the Invar samples after plane grinding were measured. The experimental results indicate that clear tension stress exists in the surface of Invar alloy along the grinding direction, while, on the cross direction, the states of surface residual stresses are complicated and affected by the parameters of grinding. A typical disk model has been calculated and analyzed by Finite Element Method (FEM), and the deformation caused by surface residual stress was presented. Finally, the effect of grinding as final working procedure on the stability of Invar structure was estimated.

Abstract: Among the properties of polishing pad, the surface roughness plays a crucial role in CMP (Chemical Mechanical Planarization) process. However, there is no acknowledged standard for measuring and characterizing the roughness of pad surface in 3D measurement. In this paper Talysurf CLI 2000 working on the principle of dynamic confocal measurement was initially suggested to measure the 3D surface topography of polishing pads through theoretical and experimental analysis. In addition, based on the Nyquist folding frequency and the statistical theory, a selection technique for sampling interval and sampling area was proposed and verified through experiments. The results showed that Talysurf CLI 2000 is more suitable than NewView to measure the 3D surface topography of polishing pads. 2μm sampling interval, 0.5×0.5mm2 sampling area and 10μm interval, 1×1mm2 area are respectively recommended for IC1000/SubaIV and SubaIV polishing pad.

Abstract: Chemical mechanical polishing (CMP) has been extensively used in the integrate circuit (IC) manufacturing industry as a widely accepted global planarization technology, accurate in situ endpoint detection of CMP process can reduce the product variance, significantly improve yield and throughput. A CMP in situ endpoint detection system, which measured the friction and downforce during CMP process using a specially designed three-axis strain gauge force sensor, was developed. The frictional transition from copper (Cu) to tantalum (Ta) barrier as well as Ta barrier to silicon dioxide (SiO2) dielectric was detected during CMP process. The experimental results showed that the change of friction could be detected when the polished material changed. The developed CMP in situ endpoint detection system is feasible for 300 mm and 450 mm copper CMP process.

Abstract: Although various diamond polishing techniques have been studied for many years, no individual method can polish free-standing CVD diamond film with high efficiency and high polishing quality. This paper investigates polishing CVD diamond film by the combination of electro-discharge machining (EDM) and chemical mechanical polishing (CMP). Scanning electro microscopy, Optical microscopy, Energy dispersive X-ray analysis, Talysurf surface profiler and Raman spectroscopy were used to evaluate the surface integrity and quality of diamond film before and after polishing. Based on the experimental results, the material removal during EDM process can be a chemo-mechanical process, including gasification, melting, sputtering, oxidation and graphitization. While in CMP process, diamond was removed under the mechanical and tribochemical interaction. The combination of EDM and CMP has advantages of high efficiency, high polishing quality and low damage. It is suitable to polish large area free-standing CVD diamond film.

Abstract: MgO single crystal is mainly used as substrate for high temperature superconductor film. Surface quality of MgO substrate has significant effect on the function of high temperature superconductor film. MgO single crystal is a typical hard and brittle material, and is easily cleaved along the {100} face, so some defects are always generated on the substrate surface while lapping and polishing, which badly affects the surface quality of the substrate. In this paper, a kind of typical defect, the triangular fracture defect which is on the substrate surface after lapping and polishing, is analyzed in detail. According to the structure characteristics of the MgO single crystal, and based on the dislocation reaction theory, a formation mechanism of the triangular fracture defect in lapping and polishing processes is explored. Through the single grain scratch test in different directions on the polished surface of MgO{100} single crystal substrates, the formation mechanism of triangular fracture defect in lapping and polishing processes is verified. And during the scratch test, the plastic flow of the MgO single crystal material beside the scratch was observed.