Papers by Author: Dong Ming Guo

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: The components of material removal in wafer Chemical mechanical polishing (CMP) was described qualitatively based on theory of corrosive wear. The value of each component was obtained by a series of wafer CMP experiments. According to analyzing the experiment results, some conclusions are obtained as follows. There is an optimum polish velocity in wafer CMP at a certain parameter. Under the optimum velocity, the balance of interaction between the mechanical action and the chemical action is reached and the material removal rate approaches maximum. The wafer CMP is a changeful and dynamic process. It cannot be obtained ideal effect of material removal by increasing the mechanical action or chemical action only. The MRR in wafer CMP mainly depends on the interaction result between the mechanical action and the chemical action and the interaction made by abrasives is a decisive part. These results provide a theoretical guide to further understanding the material removal mechanism in wafer CMP.

Abstract: An extended Time Petri Net with condition information (ECTPN) is presented in this paper including two new attributes associated to place and transition that respectively represent input condition set and output condition set. Using the model can achieve multitask cooperation and competition and let token be able to select next transaction path according to inner information. Firstly, the Time Petri Net is introduced, and then a formal semantic meaning for ECTPN in terms of input and output items is defined. Finally, we give the denotation of ECTPN. Application shows that the ECTPN validate by using business modeling.

Abstract: The calculating model of surface non-uniformity of polishing pad and the kinematical model between polishing pad and conditioner are initially established. Then the effects of several conditioning parameters were investigated by using the two models. The results of simulation and calculation show that the width ratio of diamond band of conditoner and the rotation speed at the same speed ratio between pad and conditioner have little effect on the surface non-uniformity of polishing pad, while at high non-integer rotation speed ratio, the surface non-uniformity of polishing pad is better than that at low integer speed ratio. The research results are available to select appropriate conditioning parameters especially for the stringent requirement of within-wafer non-uniformity in next generation IC.

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: An innovative fixed abrasive grinding process of chemo-mechanical grinding (CMG) by using soft abrasive grinding wheel (SAGW) has been recently proposed to achieve a damage-free ground workpiece surface. The basic principle, ideas and characteristics of CMG with SAGW are briefly introduced in this paper. The CMG experiments using newly developed SAGW for Si wafer are conducted at the condition of dry grinding. The grinding performances are evaluated and analyzed in terms of surface roughness, surface topography and surface/subsurface damage of ground wafer by use of Zygo interferometer, Scan Introduction ning Electron Microscope (SEM) and Cross-section Transmission Electron Microscope (Cross-section TEM). The component of product of ground Si surface is studied by X-ray Photoelectron Spectroscopy (XPS) to verify chemical reaction between the abrasive / additives of grinding wheel and Si wafer. The CMG process model by using SAGW is developed to understand the material removal mechanism and generation principle of damage-free surface. The study results show that the material removal mechanism of CMG by using SAGW can be explained as a hybrid process of chemical and mechanical action.

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.