Haedo Jeong

Semi-empirical material removal rate distribution model for SiO2 chemical mechanical polishing (CMP) processes

Abstract A novel semi-empirical model was developed for predicting the material removal rate (MRR) during chemical mechanical polishing (CMP) based on the following assumptions: plastic contact at the wafer–particle interface, elastic contact at the pad–particle interface, a particle size distribution, and a randomly distributed surface roughness of the polishing pad. The proposed model incorporates the effects of particle size, concentration, and distribution, as well as the slurry flow rate, pad surface topography, material properties, and chemical reactions during the silicon dioxide (SiO 2 ) CMP. To obtain the unknown parameters and ensure the validity of the model, a SiO 2 CMP experiment was conducted by using various-sized CMP slurries. The spatial distribution of the MRRs is expressed with respect to the normal contact stress distribution and the relative velocity distribution. The proposed MRR model can be used for the development of a CMP simulator, the optimization of CMP process parameters, and the design of next-generation CMP machines.

Development of a sensor information integrated expert system for optimizing die polishing

Abstract This paper presents a polishing expert system integrated with sensor information which can modify the polishing sequence and conditions initially set by the system using the on-site polishing status detected. A practical system using AE sensors is developed for rotational and curved-surface polishing. A database and a knowledge base for polishing processes are established by using the results of experiments and also experts experience. Evaluations are performed for a die of an automobile headlight lamp by using both the sensor-integrated expert system and the expert system without sensor. The results show that the sensor-integrated expert system provides more optimal polishing conditions since the proposed system takes advantage of the on-line sensor information.

Evaluation of micro-replication technology using silicone rubber molds and its applications

Micro-replication technology (MRT) originated in semiconductor processes and has been widely utilized in other industries such as sensors, micro-fluidics and displays. Recently, however, MRT has been slow in spreading due to its high cost and material limitations. Therefore, a new process in this paper, for MRT using silicone rubber molds is introduced. In this process, a silicone rubber mold transfers a master pattern to the final product with the same shape but different material. In order to verify the possibility of applying silicone rubber molds to MRT, its transferability was evaluated, and then was applied to the fabrication of PDP barrier ribs.

Self-conditioning of encapsulated abrasive pad in chemical mechanical polishing

Abstract Chemical mechanical polishing (CMP) is the process of planarization which was achieved by both chemical reaction and mechanical force. The polishing consists of moving wafer to be polished against the polyurethane pad, carrying slurry between wafer and polyurethane pad. There have been, however, some problems including dishing, erosion, high cost of consumables, environmental problems and scratches due to diamonds dropped out of conditioner. In particular, the slurry used in CMP not only increases the cost of consumables, but also interferes with the environmentally benign semiconductor manufacturing. This paper introduces the encapsulated abrasive pad to achieve the environmentally benign CMP and self-conditioning mechanism of pad. The self-conditioning just means that additive conditioning process on pad is not necessary between polishing wafers. Hydrophilic polymers were used to develop the encapsulated abrasive pad. When these polymers keep in contact with water, they have soluble and swelling characteristics. The removal rate of the encapsulated abrasive pad showed higher than that of general CMP process using slurry and polyurethane pad. The self-conditioning of pad was verified through experiment, which showed the possibility of environmentally benign process only using de-ionized water in interlayer dielectric CMP.

Investigation of Pad Surface Topography Distribution for Material Removal Uniformity in CMP Process

This paper investigates the pad surface topography distribution and its effect on material removal uniformity using two different types of conditioners in an interlayer dielectric chemical mechanical planarization (CMP) process. The two types of conditioners are a random diamond disk and a uniform diamond disk (UDD). The pad surface was roughened by using the two diamond disks, and then the surface roughness and real contact area between the pad and the wafer were analyzed. The UDD generated a more uniform surface layer having a low standard deviation, although it had a low surface roughness. The random roughness pad showed a low material removal rate with a wide standard deviation, but the uniform roughness pad demonstrated a high removal rate with a narrow standard deviation. The uniform roughness pad improved the wettability of the pad and uniform distribution of the slurry across the pad. Therefore, the uniform roughness pad gave a more stable polishing performance than the random roughness pad.

Study on heat transfer in super-high-speed grinding: energy partition to the workpiece in HEDG

Abstract Based on an analytical thermal model for deep grinding, in which the effect of the inclined angle ϕ of the heat source plane to its moving direction is taken into account, the relations of workpiece energy partition e to relevant grinding parameters are obtained. It is suggested that the inclined angle ϕ, grinding speed and also work feed all have strong influences on the energy partition to the workpiece. From the viewpoint of reducing the value e, a higher grinding speed, lower feed speed, relatively shallow cut and larger wheel size should be selected.

Effect of Process Parameters on Friction Force and Material Removal in Oxide Chemical Mechanical Polishing

The relationship between sliding friction and material removal was investigated using a sensor to measure dynamic friction force according to process parameters such as pressure, velocity, conditioning, abrasive concentration, and slurry pH during oxide chemical mechanical polishing (CMP). Friction force and material removal linearly depend on applied load and relative velocity. A high relative velocity also has an effect on the boundary condition between the wafer and the pad, and friction force reduces with increase in relative velocity. Friction force reduces with polishing time during oxide CMP with ex situ conditioning because of the changes in pad roughness parameters such as Ra, Rp, Rpk, and Rsk. Thus, the in situ conditioning method increases removal rate and improves nonuniformity. Friction force can be uniformly distributed on the oxide wafer as abrasive concentration increases owing to the reduction in friction force loaded on one abrasive particle, improving the nonuniformity of removal rate. In oxide CMP using alkali-based slurry, the effective formation and mechanical removal of the Si–OH bond layer on the SiO2 surface also affect the temporal decrease in friction force and result in a higher removal rate, in comparison with the results of a high friction force and a low removal rate in oxide CMP using neutral-based slurry.

Pad Characterization and Experimental Analysis of Pad Wear Effect on Material Removal Uniformity in Chemical Mechanical Polishing

In this study, we investigated the effects of pad wear on the nonuniformity of material removal in chemical mechanical polishing (CMP). In order to verify the mechanical aspect of the material removal mechanism, pad characterization was conducted. Pad conditioning plays a key role in obtaining stable material removal during polishing. However, the polishing pad is gradually worn as conditioning proceeds during CMP. The pad profile was measured using the contact profile measuring system to analyze pad wear after each polishing run. From experimental results, the within wafer nonuniformity (WIWNU) was unstable at the initial polishing run because of the first wafer effect. In addition, the WIWNU deteriorated as determined from a polishing pad worn by conditioning. Therefore, pad wear has a significant effect on the nonuniformity of material removal in CMP.

Effects of OH Radicals on Formation of Cu Oxide and Polishing Performance in Cu Chemical Mechanical Polishing

The amount of OH radicals generated varied according to the complexing agent or Cu ion, and the accelerating effect of OH radicals on the rate of Cu oxide formation was found in acidic pH. When Cu(I) ions and oxalic acid were added to H 2 O 2 -based slurry, the decreases in etch and removal rates of Cu were observed because more generation of OH radicals resulted in the formation of thicker Cu oxide compared to additive-free slurry. Therefore, proper control of the formation and dissolution of Cu oxide led to an increase in etch and removal rates.

Evaluation of oxide-chemical mechanical polishing characteristics using ceria-mixed abrasive slurry

Chemical-mechanical polishing (CMP) characteristics of mixed abrasive slurry (MAS) were studied which was retreated by adding of Ceria (CeO2) abrasives within 1:10 diluted silica slurry (DSS). The slurry was designed for optimal performance which produces reasonable removal rate, acceptable polishing selectivity with respect to underlying layer, low surface defects after polishing, and good slurry stability. The modified abrasives in MAS are evaluated with respect to their particle size distribution, surface morphology, and CMP performances such as removal rate and non-uniformity. As an experimental result, we could obtain successful slurry characteristics compared with traditional silica slurry in the viewpoint of removal rate and non-uniformity.