Advanced Materials Research Vols. 53-54

Abstract: Chemical mechanical polishing (CMP) has already become a mainstream technology in global planarization of wafer. The nonuniformity of material removal on wafer surface has a main influence on surface profile of silicon wafer in CMP process. However, the formation mechanism of nonuniformity in wafer CMP has not been fully understood and the influences of CMP process variables on nonuniformity are not fully clear. The nonuniformity of material removal on wafer surface has not been fully understood and the influences of CMP process variables on nonuniformity are not fully clear in CMP process. In this paper, firstly, the equation of particle movement trajectories on wafer surface was built by the movement relationship between the wafer and the polishing pad on a single head CMP machine with line oscillation of carrier. Then the distribution of abrasive trajectories on wafer surface was analyzed at different rotational speed. By the analysis, the relationship between the movement variables of the CMP machine and the With-In-Wafer Nonuniformity (WIWNU) of material removal on wafer surface had been derived. Last, the WIWNU tests were conducted on CP-4 machine. The analysis results are in accord with experimental results. The results will provide some theoretical guide for designing the CMP equipment, selecting the movement variables in CMP and further understanding the material removal mechanism in wafer CMP.

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: Studies on chemical mechanical polishing (CMP) for silicon nitride (Si3N4) balls with CeO2 abrasive carried to investigate the mechanism of chemo-mechanical action between silicon nitride and CeO2. It is found that CeO2 is more effective to obtain smooth Si3N4 balls than other abrasives, and extremely smooth Si3N4 balls with surface Ra 4nm were obtained after polishing. XRD test is used to detect the reaction resultants on the ball surface, and the results show that SiO2 is the main resultant of the chemical reaction between Si3N4 and CeO2, and the test results confirm the correctness of thermodynamic analysis based on Gibb’s free energy of formation. It is also found that water play as a key factor in CMP.

Abstract: It is very difficult matter that polishes the internal surface of the pipe, especially to the thin pipe with the traditional surface technology. Because a usual tool cannot into the inner surface of the thin pipe and automation do not achieved easily. This paper brings up a new method that utilize the characteristic of the magnetic force line may penetrate the non-magnetic material, may using the magnetic abrasive finishing (MAF) method complete to the inner surface of the thin pipe precise polishing. The magnetic abrasive finishing does not need special equipment to complete the complex shape internal surface polishing. Moreover, we already obtained the famous processing effect through the experiment. Meanwhile this paper analyses some factors of influences efficiency, and propose some solution method.

Abstract: The amorphous Ni-Pd-P alloy films with superior property have good heat conductivity and wear performance. They are widely used in the protecting coating. Copper has been chosen to be a substrate material of the produce of amorphous Ni-Pd-P alloy films with its unique electrical properties. The precision lapping technology for the copper substrate using semi-bonded abrasive grinding plate is studied in this paper. The influences of the different lapping parameters on the surface roughness, material removal rate on copper substrate surface formation in the precision lapping process are both discussed. Experimental results indicate that the copper substrate can be efficiently processed by 800# SiC semi-bonded abrasive grinding plate of, and the initial roughness of a machined surface could be improved from 0.553μm Ra to 0.28μm in 10min, yielding a ideal rarely scratch surface.

Abstract: To study the sphere-shaping mechanism under dual rotating plates (DRP) lapping mode for ceramic balls, the uniformity of lapping trace distribution is focused in this paper. Methods for simulation and evaluation of the lapping trace uniformity are proposed, and the effect of velocity parameters on the lapping uniformity of ball under DRP lapping mode is analyzed. It is found that the lapping uniformity is dependent not only on the variation range of spin angle θ, but also on the spin angle speed ωb and on the variation form of θ. The analysis results indicate that the effect of amplitude of the speed ratio function on the lapping uniformity is much greater than the effect of phase on that. When the ratio of the inner plate speed to the outer varies from 0 to2, the best lapping uniformity is obtained under the conditions demanded by this paper.

Abstract: A new plate polishing technique with an instantaneous tiny-grinding wheel cluster based on the magnetorheological (MR) effect is presented in this paper, and some experiments were conducted to prove its effectiveness and applicability. Under certain experimental condition, the material removal rate was improved by a factor of 20.84% as compared with the conventional polishing methods with dissociative abrasive particles, while the surface roughness of the workpiece was not obviously increased. Furthermore, the composite of the MR fluid was optimized to obtain the best polishing performance. On the basis of the experimental results, the material removal model of the new plate polishing technique was presented.

Abstract: The semibonded abrasive machining technique is expected to get high surface integrity and processing efficiency attributed to the „trap‟ effect which can reduce or even eliminate the surface damage induced by the larger particles. The goal of the work is to validate the „trap‟ effect by the experiments of semibonded and loose abrasive machining under the conditions of adding and not adding the larger particles. Free surface damage monocrystal silicon wafers after polishing are adopted as workpieces, and 1000# SiC as abrasive particles while 180# SiC as the larger particles. The cast iron plate is used as grinding plate in the loose abrasive machining and different bond concentration semibonded abrasive grinding plate SSB-1 and SSB-2 are used as grinding plates in semibonded abrasive machining. The roughness Rv and SEM photos of workpieces surface are tested to evaluate the extent of „trap‟ effect. The result shows that the semibonded abrasive grinding plate has the „trap‟ effect. The shore hardness value of the semibonded abrasive grinding plate can be used to be one parameter to evaluate the degree of the ‟trap‟ effect of the semibonded abrasive grinding plate.

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: This work aims to obtain fine surface of silicon wafer during precision and ultra precision machining, and presents a new method called semibonded abrasive machining. A semibonded abrasive grinding plate is used in the semibonded abrasive machining. Abrasive particle of 1000# Green SiC and bond named SSB are adopted in the manufacture of the plate. Four plates with different concentration of bond which are 1.5%, 2.5%, 3.5%, 4.5% respectively are made. The paper studies the effect of concentration of bond, the control parameters which include the lapping time, the load, and the rotating velocity of the plate on the surface roughness. Experimental results indicate each plate with different concentration of bond can obtain fine surface roughness. When the load or the rotating velocity increases, there is little effect on the surface roughness, but the material removal rate increases correspondingly. The initial roughness of the silicon wafer surface lapping by the plate could be improved from Ra 0.2μm to Ra 0.02μm in 9 min.