Abstract: In this study, basic experiments involving machining using a rotational tool were conducted with the aim of increasing the volume of material removed rate in ductile-mode machining of Si wafers. The machining surface and machining force was compared to experimentally clarify the material removal process for a single cutting edge, the critical cutting thickness tc at which occurs of cracks was set as the machining condition. Then, the three machining modes were experimentally revealed. As the result, the ductile-mode machining surface was obtained that the total depth of cut was under less than 78.5μm on ductile-brittle-mode machining.
Abstract: The polishing process of a silicon wafer is a critical factor in the fabrication of semiconductor. Because a globally planar and mirror-like wafer surface are achieved in this process. The surface roughness in the wafer depends on the surface properties of the carrier head unit along with other machining conditions such as working velocity, polishing pad, temperature, down-force, etc. In this paper, the wafer surface is investigated according to several parameters and experimental data. Experiments were performed to observe the down-force and temperature when the wafer carrier head unit was pressed down onto the polishing pad. A loadcell was employed to obtain the signal of the applied pressure against the polishing pad. Also, working temperature was detected using an infrared sensor. To study on the optimum conditions of machining, monitoring system is coded in Ch and the results of experiment present data using Ch.
Abstract: Here we use 2-D models of fluid film lubrication and contact mechanics to calculate the contact stress and fluid (i.e., slurry) pressure distributions on the wafer–pad interface in CMP. In particular, the effective rigidity of the wafer (determined by the wafer carrier structure), the retaining ring width and its back pressure are taken to be the design parameters. The purpose is to study the synergetic effects of such parameters on the contact stress non-uniformity (NU), which directly affects the spatial non-uniformity of the material removal rate on the wafer surface. Our numerical results indicate that, for a given wafer rigidity, one may choose a particular combination of the retaining ring parameters to minimize NU. Also, the corresponding minimum NU decreases with the effective wafer rigidity, suggesting that it is beneficial to use a soft (e.g., floating-type) wafer carrier. Moreover, for a soft wafer carrier, the presence of the retaining ring also reduces NU to some extent, but the use of a multi-zone wafer-back pressure profile would be more effective in this regard.
Abstract: Chemical Mechanical Polishing(CMP) is currently the most effective planarization method used in the semiconductor industry. Because of the continuous improvement of the wafer size and line width, the CMP process must be promoted and improved. Many studies have been undertaken to try and achieve both a high material remval rate (MRR) while maintaing a high surface quality of silicon wafer, however up until this point it appears that the two objectives are mutually exclusive. In this paper, an innovative method which integrated ultrasonic vibration assisted machining and CMP (UCMP) has been developed. With the use of ultrasonic vibration, the CMP efficiency and the quality of ploished suface improves considerably as shown in this paper. The basic principle effects of ultrasonic vibration are further illustrated and the experiments had been done to demostrate the proper procedure. The results showed that UCMP achieves a higher material removal rate (MRR) and better surface quality at the same time.
Abstract: Abrasive Free Polishing (AFP) is a polishing technology without abrasives and widely employed in copper-base semiconductor fabrications. This paper investigates the effect of passivants, added to the slurry, on the material removal rate (MRR) and the non-uniformity (NU) via experiments. Two kinds of passivants, Benzotriazole (BTA) and citric acid (CA) are added to the slurry for the experiments. Experimental results showed that the MRR increases when polishing pressure increases while NU decreases at the same time. Both MRR and NU tends to increase when rotational speed increases, though MRR and NU at 40 rpm are lower than that at 30 and 50 rpm in the slurry with CA. Experimental data also showed that AFP using the slurry with CA performs better than that with BTA.
Abstract: The friction phenomenon was investigated to explore the relationship between the diamond conditioner, polishing pad and wafer of oxide film in the chemical mechanical polishing (CMP) process. Two kinds of diamond conditioners (disk-A and disk-B) were used. Diamond disk-A used was traditional diamond conditioner containing random shaped diamond grits. Diamond disk-B used was made by sculpturing a sintered polycrystalline diamond to form identically shaped cutting tips. Experimental results reveal that friction force between disk and pad increases with dressing load. But friction force decreases with sliding speed due to increase of sliding speeds resulting in an increase of interface temperature. The coefficient of friction between wafer and pad initially increases with the dressing load, and then it starts to drop slowly with further increases of the dressing load. It was found that removal rate of the oxide film correlates well with the variation of the coefficient of force. In addition disk-B can produce a higher wafer removal rate under a low dressing load.
Abstract: Sintered polycrystalline diamond cubicles were oriented to make CMP pad conditioners. The dressing experiments demonstrated the capability of fast pad cutting and efficient removal of glazed layer that is formed by polishing wafers with slurry on dressed pad.
Abstract: Diamond disks are indispensable for dressing CMP pads in the manufacture of semiconductors. Conventional diamond disks contain one type of diamond grits, with the aim to achieve two different functions, viz. glaze shaving and asperities grooving. Cocktail diamond disks are made by assembling brazed diamond pallets that contain different types of diamond crystals. Thus, the pad can be dressed clean, and at the same time, asperities may polish wafers fast without damaging.
Abstract: For the analysis of cooling effect, the cutting inserts were heated to 900°C and then exposed in the room-air and cold-air with different pressure respectively. The temperature variation were recorded by infra-red (IR) pyrometer. The temperature-dependent global heat transfer coefficients were estimated by the theoretical analysis and experimental data. The finite element analysis (FEA) was employed to simulate the cooling process and modify the estimated heat transfer coefficients. The heat transfer coefficients decreased from 55.1 W/m2•°C (800°C) to 9.32 W/m2•°C (350°C) in the natural cooling and approximately 300 W/m2•°C (600°C) to 60 W/m2•°C (300°C) in the cold-air cooling. Cold-air cooling greatly increased the heat transfer coefficients, but it seemed the air pressure had little pressure on the heat transfer coefficients.
Abstract: Machining is one of the most important processes in producing automotive component such as difficult-to-cut FCD700 cast iron grade. Efforts are continuously made to improve the machining technique for the benefit of human and environment. This paper presents an environmental friendly when turning FCD700 cast iron using carbide tool in the absent of coolant. The turning process was carried out in three medium of dry conditions i.e. without air, chilled air and normal air. The turning parameters studied were cutting speed (100-300 m/min), feed rate (0.1-0.4 mm/rev), and depth of cut (0.2-2.0 mm). Result shows that the average surface roughness (Ra) was greatly affected by the feed rate and the effect of depth of cut was negligible. Low Ra value was produced when using high cutting speed, especially at medium air temperature of 10 deg C. Whereas when turning at high depth of cut and high feed rate, the tool life was shorten drastically. In addition, the cutting speed was significantly affecting the tool life. The tool life was found to be inversely proportional with the cutting speed. The longest tool life was obtained at cutting speed of 100 m/min, feed rate of 0.15 mm/rev, depth of cut of 0.2 mm and temperature of -2 deg C. Generally, chilled air at temperature of -2deg C will increase the tool life, but the Ra obtained was deteriorated when compared at higher temperature of chilled air and without air cutting environment. Therefore, these findings can be used a guide depending on the preference of the user, either to obtain a better tool life or Ra value.