The influence of ultrasonic vibrations on material removal in the silicon wafer polishing using DDCAMRF: Experimental investigations and process optimization

Author(s):  
Mayank Srivastava ◽  
Pulak M Pandey

The present experimental investigation attempts to understand and address the effect of ultrasonic vibrations on material removal in the polishing of silicon wafers (1 0 0). The requisite finishing experimentations were performed on an indigenously developed experimental arrangement of double-disc chemical assisted magnetorheological finishing (DDCAMRF) process with longitudinal vibrations. The MR fluid used in the experiments consists of a water-based suspension prepared by mixing suitable amounts of carbonyl iron particles (CIPs), abrasive particles, and additives or stabilizers. The prepared MR fluid uses both mechanics and chemistry to finish the silicon surface. Mechanics is mainly responsible for micro-scratching of silicon surface, which gets “softened” by hydration utilizing DI water in the MR fluid. In this study, the ‘response surface methodology (RSM)’ was chosen for designing the experiments to evaluate the significance of different process factors, namely polishing speed, abrasive concentration, and ultrasonic power on the material removal rate (MRR) in DDCAMRF process. The material removed from the wafer surface was measured using the precision digital weighing balance. It was observed that the MRR was found to increase with the increase in various process factors used. Further, analysis of variance (i.e., ANOVA) technique with a 95% confidence interval was performed to analyze the significant contribution of different process factors on MRR. The validation of developed model was done by performing experiments on random and optimized set of process factors. From, the statistical investigation it was discovered that ultrasonic power has highest contribution of 57.9% on MRR, followed by the polishing speed (13.3%), and abrasive concentration (12.5%). Furthermore, a genetic algorithm optimization tool was utilized to obtain optimum set of process parameters to maximize MRR.

Author(s):  
Chunhui Chung ◽  
Glenn Melendez ◽  
Imin Kao

Wafers made of materials such as silicon, III-V and II-VI compounds, and optoelectronic materials, require high-degree of surface quality in order to increase the yield in micro-electronics fabrication to produce IC chips and devices. Measures of properties of surface quality of wafers include: nanotopography, surface morphology, global planarization, total thickness variation (TTV) and warp. Due to the reduction of feature size in micro-electronics fabrication, the requirements of such properties become more and more stringent. To meet such requirements, the wafer manufacturing processes of brittle semiconductor materials, such as slicing, lapping, grinding, and polishing have been continually improved. In this paper, the lapping process of wafer surface treatment is studied with experimental results of surface roughness and material removal rate. In order to improve the performance of lapping process, effects of mixed abrasive grits in the slurry of the free abrasive machining (FAM) processes are studied using a single-sided wafer-lapping machine. Under the same slurry density, experiments employing different mixing ratios of large and small abrasive grits, and various normal loadings on the wafer surface applied through a jig are conducted for parameter study. With various mixing ratios and loadings, observations and measurements such as the total amount of material removed, material removal rate, surface roughness, and relative angular velocity are presented and discussed in this paper. The experiments show that the half-half mixing ratio of abrasives removes more material than other mixing ratios under the same conditions, but with a higher surface roughness. The results of this study can provide a good reference to the FAM processes that practitioners use today by exploiting different mixing ratios and loadings of abrasive slurry in the manufacturing processes.


2011 ◽  
Vol 3 (5) ◽  
pp. 211-213
Author(s):  
Dr. G.Harinath Gowd ◽  
◽  
M. Gunasekhar Reddy ◽  
Bathina Sreenivasulu ◽  
Rayudu Peyyala

Author(s):  
Harsha Goel ◽  
Pulak M Pandey

The article describes fabrication of an experimental setup which could be used for electrochemical drilling process to produce micro-holes in a copper workpiece with its different variants, namely, jet electrochemical micro-drilling, air-assisted jet electrochemical micro-drilling, ultrasonic-assisted jet electrochemical micro-drilling, and pulsed direct current–jet electrochemical micro-drilling process. Process parameters like voltage, electrolyte concentration, interelectrode gap, and electrolyte pressure have been selected to find out their effects on the process responses, namely, hole taper and material removal rate in all the above process. Attachments for air assistance and ultrasonic vibration application have been fabricated and incorporated in the setup. The effects of ultrasonic vibrations and the pulsed direct current voltage on the process responses like material removal rate and hole taper have been investigated. The effect of application of ultrasonic vibrations on the electrolyte jet has been studied. The experimental findings of ultrasonic-assisted jet electrochemical micro-drilling were compared with the findings of jet electrochemical micro-drilling. Similarly, the findings of pulsed direct current–jet electrochemical micro-drilling were also compared with the results of pulsed direct current ultrasonic-assisted jet electrochemical micro-drilling experiments. It has been found that the ultrasonic vibrations have significant effect on the two process responses. From the results, it was observed that with the use of ultrasonic vibrations, the material removal rate has increased to significant level and the hole taper has been decreased than in jet electrochemical micro-drilling. Effects of the pulsed direct current voltage supply on jet electrochemical micro-drilling and (ultrasonic-assisted jet electrochemical micro-drilling) were also analyzed. Application of pulsed direct current voltage has improved the material removal rate and reduced the hole taper in jet electrochemical micro-drilling as well as in ultrasonic-assisted jet electrochemical micro-drilling. The experimental results concluded that ultrasonic assistance have generated the holes with greater material removal rate and lower hole taper and with continuous direct current and pulsed direct current voltage.


2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Prasad D. Unde ◽  
M. D. Gayakwad ◽  
N. G. Patil ◽  
R. S. Pawade ◽  
D. G. Thakur ◽  
...  

Abrasive waterjet machining (AWJM) is an emerging machining process in which the material removal takes place due to abrasion. A stream of abrasive particles mixed with filtered water is subjected to the work surface with high velocity. The present study is focused on the experimental research and evaluation of the abrasive waterjet machining process in order to evaluate the technological factors affecting the machining quality of CFRP laminate using response surface methodology. The standoff distance, feed rate, and jet pressure were found to affect kerf taper, delamination, material removal rate, and surface roughness. The material related parameter, orientation of fiber, has been also found to affect the machining performance. The kerf taper was found to be 0.029 for 45° fiber orientation whereas it was 0.036 and 0.038 for 60° and 90°, respectively. The material removal rate is 18.95 mm3/sec for 45° fiber orientation compared to 18.26 mm3/sec for 60° and 17.4 mm3/sec for 90° fiber orientation. The Ra value for 45° fiber orientation is 4.911 µm and for 60° and 90° fiber orientation it is 4.927 µm and 4.974 µm, respectively. Delamination factor is found to be more for 45° fiber orientation, that is, 2.238, but for 60° and 90° it is 2.029 and 2.196, respectively.


2005 ◽  
Vol 127 (1) ◽  
pp. 190-197 ◽  
Author(s):  
Yeau-Ren Jeng ◽  
Pay-Yau Huang

Chemical Mechanical Polishing (CMP) is a highly effective technique for planarizing wafer surfaces. Consequently, considerable research has been conducted into its associated material removal mechanisms. The present study proposes a CMP material removal rate model based upon a micro-contact model which considers the effects of the abrasive particles located between the polishing interfaces, thereby the down force applied on the wafer is carried both by the deformation of the polishing pad asperities and by the penetration of the abrasive particles. It is shown that the current theoretical results are in good agreement with the experimental data published previously. In addition to such operational parameters as the applied down force, the present study also considers consumable parameters rarely investigated by previous models based on the Preston equation, including wafer surface hardness, slurry particle size, and slurry concentration. This study also provides physical insights into the interfacial phenomena not discussed by previous models, which ignored the effects of abrasive particles between the polishing interfaces during force balancing.


2010 ◽  
Vol 126-128 ◽  
pp. 475-480 ◽  
Author(s):  
Yin Biao Guo ◽  
Wei Yang ◽  
Zhen Chen ◽  
Yun Feng Peng

In this paper, the with-in-wafer non-uniformity (WIWNU) of the lager quadrate optic in the fast polishing process (FPP) is discussed from the machine side. At the machine side, the non-uniform stress on the wafer surface is the major reason for the non-uniform material removal rate which results in the WIWNU. Stresses arise mainly from two sources, namely the pressure exerted by the polishing pad and shear stress due to the relative motion between the wafer and pad. Based on the special chemical mechanical polishing FPP, the kinematic motion of the wafer is analyzed and the non-uniform stress is analyzed by a 3D axisymmetric quasi-static model. The WIWNU can be reduced by adjusting the stress.


2010 ◽  
Vol 135 ◽  
pp. 18-23 ◽  
Author(s):  
Qiu Sheng Yan ◽  
Jie Wen Yan ◽  
Jia Bin Lu ◽  
Wei Qiang Gao

A new planarization polishing method based on the cluster magnetorheological (MR) effect is presented to polish optical glass in this paper. Some process experiments were conducted to reveal the influence of the content of carbonyl iron and the abrasive materials in the MR fluid on the machining effect, and the machining characteristic of polished surface was studied. The results indicate that the surface roughness of the polished workpiece can be reduced rapidly when the strong magnetic field is applied, and ultra smooth surface with Ra 1.4 nm can be achieved while the CeO2 abrasives are used in the MR fluid. The content of carbonyl iron obviously influences the machining effect of this planarization polishing method based on cluster MR-effect. With the increase of the content of carbonyl iron in the MR fluid, the material removal rate improves and the surface roughness reduces rapidly. However, the difference of abrasive material results in various machining effects. As for the K9 optical glass, the CeO2 abrasive is better polishing abrasive than the SiC abrasive in the planarization polishing technique based on the cluster MR-effect.


Author(s):  
Ravi Pratap Singh ◽  
Sandeep Singhal

Macor ceramic has been well recognized as an eminent engineering material which possesses enlarged industrial usage owing to its excellent and versatile properties. However, its fruitful and economic processing is still unanswered. This article has targeted to experimentally investigate the influence of numerous process variables on machining characteristics in rotary ultrasonic machining of Macor ceramic. The impact of different input factors, namely, spindle speed, feed rate, coolant pressure, and ultrasonic power has been appraised on process responses of interest, that is, material removal rate and chipping size. The experimental plan was designed by employing response surface methodology through central composite rotatable design. The variance analysis test has also been performed with a view to observe the significance of considered parameters. Microstructure of machined samples has also been evaluated and analyzed using scanning electron microscope. This analysis has revealed and confirmed the presence of dominated brittle fracture that caused removal of material along with the thin plastic deformation in rotary ultrasonic machining of Macor ceramic. The reliability and competence of the developed mathematical model have been established with test results. The multi-response optimization of machining responses has also been done by utilizing desirability approach, and at optimized parametric setting, the obtained experimental values for material removal rate and chipping size are 0.4762 mm3/s and 0.3718 mm, respectively, with the combined desirability index value of 0.937.


1991 ◽  
Vol 113 (1) ◽  
pp. 75-84 ◽  
Author(s):  
V. K. Jain ◽  
P. Sreenivasa Rao ◽  
S. K. Choudhary ◽  
K. P. Rajurkar

Fiber reinforced composites, though relatively new, have already become important engineering materials. So far the main emphasis of research has been on the development of materials, but nowadays more attention is being paid to the industrial manufacture of products made of composites. Conventional machining methods and some unconventional machining methods like laser beam machining (LBM) and water jet machining (WJM) cannot be effectively applied for machining of composites due to the resulting problems of air borne dust, tool wear, and thermal damage. Recently electrochemical spark machining (ECSM) has been applied for the cutting and drilling of holes in composites. The success achieved in the application of ECSM for cutting of composites has stimulated interest in exploring the prospects of use of traveling wire electrochemical spark machining (TW-ECSM) process for cutting of composites. An apparatus for TW-ECSM is designed and fabricated in the laboratory. The results about the feasibility of the process and its performance during machining of composites are presented in this paper. Experiments are carried out on glass-epoxy and kevlar-epoxy composites, using sodium hydroxide (NaOH) as electrolyte. The wire and the workpiece were kept in physical contact with each other by the use of a gravity feed mechanism. The effects of voltage and concentration of the electrolyte on material removal rate, average diametral overcut, tool wear rate, and wire erosion ratio are reported. The theoretical analysis of the mechanism of the process identifies the thermo-mechanical phenomena as the main source of material removal in ECSM.


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