Hyoung Jae Kim

The Effect of Mixed Abrasive Slurry on CMP of 6H-SiC Substrate

Silicon carbide (SiC) is a wide band gap semiconductor being developed for high temperature, high power, and high frequency device applications. For the manufacturing of SiC to semiconductor substrate, many researchers have studied on the subject of SiC polishing. However, SiC faces many challenges for wafer preparation prior to epitaxial growth due to its high hardness and remarkable chemical inertness. A smooth and defect free substrate surface is important for obtaining good epitaxial layers. Therefore, hybrid process, chemical mechanical polishing (CMP) has been proposed to achieve epi-ready surface. In this paper, the material removal rate (MRR) is investigated to recognize how long the CMP process continues to remove a damaged layer by mechanical polishing using 100 nm sized diamond, and the authors tried to find the dependency of mechanical factors such as pressure, velocity and abrasive concentration using single abrasive slurry (SAS). Especially, the authors tried to get an epi-ready surface with mixed abrasive slurry (MAS). The addition of the 25nm sized diamond in MAS provided strong synergy between mechanical and chemical effects resulting in low subsurface damage. Through experiments with SAS and MAS, it was found that chemical effect (KOH based) was essential and atomic-bit mechanical removal was efficient to remove residual scratches in MAS. This paper concluded that SiC CMP mechanism was quite different from that of relatively soft material to achieve both of high quality surface and MRR.

Pad Surface Characterization and its Effect on the Tribological State in Chemical Mechanical Polishing

An understanding of the pad surface state and its effect on the tribological regime of the polishing process is critical to understanding the fundamental mechanism of Chemical Mechanical Polishing (CMP). The focus of this study is the measurement of pad surface roughness evolution during the polishing process and its characterization, which has a critical relation to the polishing rate and decay phenomena of the polishing rate during polishing when conditioning is suspended. Research reveals that the average roughness parameters Ra or Rq have a weak relation to the removal rate, which contradicts the general idea about the relation between polishing rate and roughness. However, it was found that the reduced peak height Rpk has the most significant influence on the removal rate. Considering the theoretical concept of the real area of contact, a reasonable explanation about the phenomena is that the reduced peak height, rather than the average roughness, dominates the real area of contact. Introduction Over the last decade, chemical mechanical polishing (CMP) has been widely accepted as a breakthrough in the planarization of subhalf-micrometer integrated circuits (IC) device manufacturing [1,2]. Because of itx92s excellent planarization capacity to meet stringent lithographic requirements, CMP has been widely used for the planarization of dielectric layer (ILD; interlayer dielectric), isolation (STI; shallow trench isolation), and metallization processes (damascene). Fig.1 Schematic of CMP equipment and the component of process The CMP process is conducted by controlling the polishing pressure and the relative velocity. A rotating wafer is pressed facedown against a rotating polish pad, as depicted in Fig. 1. The wafer and the pad are usually rotated in the same direction and with the same or nearly the same angular velocity about their respective centers for the purpose of achieving an appropriate relative velocity and velocity uniformity across the wafer surface. The polishing slurry containing abrasive particles and chemical reagents is delivered near the center of the rotating polishing pad. Materials on the wafer Key Engineering Materials Online: 2004-02-15 ISSN: 1662-9795, Vols. 257-258, pp 383-388 doi:10.4028/www.scientific.net/KEM.257-258.383

The Characteristics of Frictional Behaviour in CMP Using an Integrated Monitoring System

Chemical mechanical polishing (CMP) has become the preferred technology to achieve global planarization of wafer surfaces. Especially in oxide CMP, mechanical factors have a greater effect on the removal rate than chemical factors. So, the effects of mechanical parameters in CMP can be expressed as friction force and heat caused by friction. The friction force can be evaluated by a CMP friction force monitoring system and process temperature can be obtained by an infrared rays (IR) sensor. Furthermore, friction energy can be calculated from the friction force monitoring system. In this paper, research on the correlation between frictional and thermal characteristics of SiO2 slurry and CMP results was conducted. This data, which was obtained by using integrated monitoring system for CMP, will lead to the efficient prediction of CMP results.

Energy harvesting characteristics of unimorph cantilever generator using 0.69Pb(Zr0.47Ti0.53)O3-0.31Pb(Ni0.6Zn0.4)1/3Nb2/3)O3 + 0.5 mol% CuO (PZCN) thick films under various sintering conditions

A 0.69Pb(Zr0.47Ti0.53)O3-0.31Pb(Ni0.6Zn0.4)1/3Nb2/3)O3 +0.5xa0mol% CuO (PZCN) thick films were investigated for potential use in energy harvesting device applications. The PZCN thick films were fabricated by a conventional tape casting process and sintered at various temperatures. An excellent piezoelectric properties of d33 = 470 pC/N, ε33T/ε0 =1654, kpu2009=u20090.52 and d33u2009⋅u2009g33 = 15,087u2009×u200910−15xa0m2/N were obtained film sintered at 950xa0°C that this material as a energy density material. It was also demonstrated that a unimorph cantilever using the PZCN film could generate a significant power of 7.6xa0mW (1.05xa0mW/cm2) for high performance energy harvesters.

Experimental Analysis in Lithium Niobate CMP for Room Temperature Bonding

Lithium niobate (LN, LiNbO3) is a kind of artificial crystal with piezoelectricity, pyroelectricity and ferroelectricity, which has been widely used in electron components. The large difference in thermal expansion coefficients between Si and LN causes a serious thermal stress during the thermal-pressure bonding process. Therefore room temperature bonding would be the best candidate to make strong and stress-free interface between Si and LN. However, room temperature bonding requires lower surface roughness (Ra<2nm) and lower defects on the LN wafer surface than those of thermal bonding. Chemical mechanical polishing (CMP) process helps LN to obtain the high quality surface and thin wafer suited in room temperature bonding. The LN wafer was polished using colloidal silica slurry, resulting in high material removal rate (MRR) and fine surface quality under the condition of low pH, high abrasive concentration and low flow rate. The polishing mechanism of LN was discussed by mechanical, chemical and thermal analysis.

Kinematic Analysis of Chemical Mechanical Polishing and its Effect on Polishing Results

Kinematic analysis for the conventional rotary CMP polisher was conducted a nd its effect on polishing results was assessed. The authors define a novel paramete r ζ as a kinematic index, which includes the effects of wafer size, distance between the rotati on centers, and the rotation ratio of wafer and pad. The analysis result suggests that the shape of velocity dis tribution, direction of friction force, uniformity of velocity distribution, distribution of sliding distance, and t he uniformity of sliding distance distribution could be consistently expressed in terms of the kinemat ic index ζ. These results become more important as the wafer size increases and the requir ment on the wafer nonuniformity is more stringent. Introduction As the integration density of ULSI increases, chemical mechanic al planarization (CMP) becomes one of the most important ULSI processes for the 0.25 μm generation and beyond. The main purpose of CMP is achieving both global and local planarization. Especially, globa l planarization is one of the most important factors affecting the yield of device manufacturing . There are several parameters affecting within wafer nonuniformity (WIWNU), such as pressure dis tribution over the wafer surface, relative velocity distribution, flow and chemical condition of the slurry, temperatur e distribution, the state of pad conditioning and other chemical and mechanical factors. Am ong them, relative velocity distribution on the wafer surface is considered as an important fact or affecting the spatial distribution of removal rate since it determines the sliding distance of given point on the wafer. The early work of F. W. Preston [1] and H. Hocheng [2] had analyzed some aspects of kinematics in CMP. Meanwhile, many areas still remain to be studied for anal ytical and intuitive results in kinematics of CMP. Therefore, in this study, kinematic analysis wa s executed to characterize and evaluate the effect of the rotation ratio and distance between rota tion centers upon velocity distribution and sliding distance. It is hypothesized that the material removal in CMP has a linea r dependency on sliding distance, in accordance with the Preston equation, the most widely accepted descri ption of CMP. Therefore, the amount of material removal at given point is considered to be determi ned according to the relative sliding distance of that point. Kinematic Analysis Rotary CMP equipment is most widely used in semiconductor manufacturi ng. The main purpose of these kinematic conditions of equipment is to achieve uniform removal of thin film material from the entire wafer area. It is well known that the velocity over the c ontact area between the wafer and pad surface are the same at synchronized motion of head and table, i.e. w w=wp [1]. However, because of process optimization, most of practical recipes for rotation condition are not designed for Key Engineering Materials Online: 2003-04-15 ISSN: 1662-9795, Vols. 238-239, pp 229-234 doi:10.4028/www.scientific.net/KEM.238-239.229

Influences of Polyurethane Nozzle Shape on Mixing Efficiency

For reaction injection molding (RIM) polyurethane was mixed in the mixing head by impingement mixing, injected into the mold, and cured quickly, as soon as the mold is filled. The shape of the nozzle in the mixing head is critical to improve the quality of polyurethane. To achieve homogeneous mixing, an intensive turbulence energy in the mixing nozzle is essential. In this study, a mixing nozzle for RIM was designed, and mixing efficiency was investigated based on experiment. Experiments were conducted with different combinations of nozzle tips and exit diameter to measure the mixing efficiency by measuring jet force and investigating mixing image with high speed camera. Jet force increased gradually and reaches steady state conditions. The jet force depended on shape of nozzle tip and outlet sizes. These results suggest that optimized nozzle configurations are necessary for high efficiency mixing with RIM.

Modeling and Analysis of Material Removal Characteristics in Silicon Wafer Double Side Polishing

As advancing technologies increase the demand for yield and planarity in integrated circuits, wafers have become larger and their specifications more stringent. Flatness, thickness variation and nanotopography have emerged as important concerns in the wafering process. Double side polishing has been adopted as a solution to these problems. This paper focuses on the material removal characteristics and wafer profile variation during Si double side polishing. A polishing experiment to investigate Si removal characteristics according to process parameters was carried out in a single head rotary polisher equipped with a monitoring system for friction force. It was found that the material removal rate is related to friction energy rate, and the polishing state was transited and divided into three conditions according to pressure. On the basis of the experimental results, the wafer profile variation in double side polishing was modelled and simulated according to pressure. The friction energy was calculated to find the material removal amount across the wafer. With the conversion of calculated friction energy to the material removal amount, wafer profile variation was simulated. As a result, the wafer profile variation and its range were increased with a pressure increase, and originated from the position near the wafer edge.

Two-Step Planarization of ECMP and CMP for MEMS Copper Patterns

Chemical mechanical polishing (CMP) has been used as planarization process in the fabrication of semiconductor devices. The CMP process is required to planarize the overburden film in an interconnect process by high relative velocity between head and platen, high pressure of head and chemical effects of an aqueous slurry. But, a variety of defects such as dishing, delamination and metal layer peering are caused by CMP factors such as high pressure, pad bending and strong chemical effect. The electrical energy of the electro-chemical mechanical planarization (ECMP) dissolves copper (Cu) solid into copper ions electrochemically in an aqueous electrolyte. The dissolved copper complex layer or passivation layer is removed by the mechanical abrasions of polishing pad and abrasive. Therefore the ECMP process realizes low pressure processing of soft metals to reduce defects comparing to traditional CMP process. But, if projected metal patterns were removed and not remained on whole wafer surface in final processing stage, Cu layer could not be removed by ECMP process. The two-step process consists of the ECMP and the conventional CMP used in micro patterned Cu wafers. First, the ECMP process removed several tens m of bulk copper on Cu patterned wafer within shorter process time than the Cu CMP. Next, residual Cu layer was completely removed by the Cu CMP under low pressure. Total time and process defects are extremely reduced by the two-step process.