기계적 분쇄화법으로 제조된 (Ti52Al48)100-xBx(X=0,0.5,2,5) 합금의 미세조직 및 기계적 성질

표성규,김낙준,정현호,황승준 대한금속재료학회(대한금속학회) 1998 대한금속·재료학회지 Vol.36 No.12

The present study is concerned with γ-(Ti_(52)Al_(48))_(100-x)B_x(x=0, 0.5, 2, 5) alloys produced by mechanical milling/vacuum hot pressing using melt-extracted powders. Microstructure of as-pressed alloys exhibit dual phase equiaxed microstructure of α₂ and γ with a mean grain size of 200 ㎚. Besides α₂ and γ phase, binary and 0.5%B alloys contains Ti₂AlN and Al₂O₃ phases located along the grain boundaries and show appreciable coarsening in grain and dispersoid sizes during annealing treatment at 1300℃ for 5 h. On the other hand, 2%B and 5%B alloys contains fine boride particles within the γ grains and show minimal coarsening during annealing. Room temperature compression tests of as-pressed alloys reveal low ductility, but very high yield strength >2100 ㎫. After annealing treatment, mechanically milled alloys show much higher yield strength than conventional PM and IM processed alloys, with equivalent ductility to IM processed alloys. 5%B alloy with smaller grain size shows higher yield strength than binary alloy at room temperature. When test temperature is increased to 850℃ 5%B alloy shows much lower strength than binary alloy, indicating the deformation of fine 5%B alloy is dominated by the grain boundary sliding mechanism.

기계적 분쇄화법으로 제조된 $(Ti_{52}Al_{48})_{100-x}$-xB(x=0,0.5,2,5) 합금분말의 제조 및 미세조직 특성

표성규 한국분말야금학회 1998 한국분말재료학회지 (KPMI) Vol.5 No.2

$Ti_{52}Al_{48}$ and $(Ti_{52}Al_{48})_{100-x}B_x(x=0.5, 2, 5)$ alloys have been Produced by mechanical milling in an attritor mill using prealloyed powders. Microstructure of binary $Ti_{52}Al_{48}$ powders consists of grains of hexagonal phase whose structure is very close to $Ti_2Al$. $(Ti_{52}Al_{48})_{95}B_5$ powders contains TiB2 in addition to matrix grains of hexagonal phase. The grain sizes in the as-milled powders of both alloys are nanocrystalline. The mechanically alloyed powders were consolidated by vacuum hot pressing (VHP) at 100$0^{\circ}C$ for 2 hours, resulting in a material which is fully dense. Microstructure of consolidated binary alloy consists of $\gamma$-TiAl phase with dispersions of $Ti_2AlN$ and $A1_2O_3$ phases located along the grain boundaries. Binary alloy shows a significant coarsening in grain and dispersoid sizes. On the other hand, microstructure of B containing alloy consists of $\gamma$-TiAl grains with fine dispersions of $TiB_2$ within the grains and shows the minimal coarsening during annealing. The vacuum hot pressed billets were subjected to various heat treatments, and the mechanical properties were measured by compression testing at room temperature. Mechanically alloyed materials show much better combinations of strength and fracture strain compared with the ingot-cast TiAl, indicating the effectiveness of mechanical alloying in improving the mechanical properties.

Degradation of the Barrier Integrity of Porous Low-k Dual Damascene Interconnects Using Dual Top Hard Mask Process Integration

표성규,Sang-Young Kim 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.4

This paper reports a reliability failure mechanism in Cu/low-k dielectric dual damascene structures, which was observed under accelerated temperature stress. The Cu diffuses through the metal barrier into the low-k material, leaving voids in Cu interconnects. The proposed mechanism is one in which oxidants from the atmosphere diffuse through the low-k material and then through defects in the metal barrier to react with the Cu. The oxidation of the Cu produces a chemical potential, driving Cu from its original location out into the low-k material. The mechanism can be suppressed by improving the metal barrier's integrity and/or by excluding oxygen from the ambient. This paper reports a reliability failure mechanism in Cu/low-k dielectric dual damascene structures, which was observed under accelerated temperature stress. The Cu diffuses through the metal barrier into the low-k material, leaving voids in Cu interconnects. The proposed mechanism is one in which oxidants from the atmosphere diffuse through the low-k material and then through defects in the metal barrier to react with the Cu. The oxidation of the Cu produces a chemical potential, driving Cu from its original location out into the low-k material. The mechanism can be suppressed by improving the metal barrier's integrity and/or by excluding oxygen from the ambient.

기계적 합금화법으로 제조된 (Ti52Al48)100-xBx 합금의 미세조직 형성과정

표성규,김낙준,정현호,김상혁,황승준 대한금속재료학회(대한금속학회) 1998 대한금속·재료학회지 Vol.36 No.11

The main objective of this study is to investigate the microstructural evolution during mechanical milling of prealloyed (Ti_(52)Al_(48))_(100-x)B_x powders and also to investigate the effects of B contents and heat treatment on the microstructure of mechanically milled TiAl alloys. Microstructure of binary Ti_(52)Al_(48) Powders consists of grains of hexagonal phase whose structure is very close to Ti₂Al. (Ti_(52)Al_(48))_(95)B_5 powders contain TiB₂ in addition to matrix grains of hexagonal phase. The grain sizes in the as-milled powders of both alloys are nanocrystalline. The mechanically alloyed powders were consolidated by vacuum hot pressing (VHP) at 1000℃ for 2 hours, resulting in a material which is fully dense. Microstructure of consolidated binary alloy consists of γ-TiAl phase with dispersions of Ti₂AlN and A1₂O₃ phases located along the grain boundaries. Binary alloy shows a significant coarsening in grain and dispersoid sizes. On the other hand, microstructure of B containing alloy consists of γ-TiAl grains with fine dispersions of TiB₂ within the grains and shows the minimal coarsening during annealing.

초 고순도 TiAl 금속화합물의 미세조직 및 변형거동에 미치는 Al 조성의 영향

표성규,김낙준,오진근,Yamaguchi, M . 대한금속재료학회(대한금속학회) 2000 대한금속·재료학회지 Vol.38 No.5

The present study is concerned with the effect of Al composition on the deformation behavior of ultra high pure (UHP) Ti-(48,50,52) at.%Al alloys using ultra high pure Ti with 30 wt. ppm oxygen. It is suggested that the deformation mechanism of UHP binary TiAl is strongly dependent on Al compositions. The deformation substructure of UHP Ti-48 at.%Al is shown to be dominated by ordinary dislocation with b = 1/2$lt;11￣0] as well as deformation twinning and small portion of 1/2$lt;112￣] superdislocation. Deformation mechanism in UHP Ti-50 at.%Al alloy consists of 1/2$lt;11￣0] type ordinary dislocation and 1/2$lt;112￣] superdislocation and a small portion of $lt;01￣1] superdislocation, but deformation twinning is not observed. Most of dislocation structure in UHP Ti-52 at.%Al alloy consisted of the faulted dipoles. Major deformation mode of UHP Ti-48 at.%Al and UHP Ti-50 at.%Al alloys was ordinary dislocation in deformation orientation, which take an advantage of ordinary dislocation slip. However, the major deformation of UHP Ti-52 at.%Al alloys was superdislocation slip in this orientation. It seems that there is little difference between major deformation mode of nominal purity TiAl and that of TiAl contained ultra low oxygen.

Ti-(43-54)Al-xMn-yNb(x=0,3,4, y=0,4) 합금의 미세조직 및 변형거동 (1) : 미세조직 및 기계적 성질

표성규,김낙준,오진근 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.11

The main objective of the present paper is to study the effect of heat treatment and temperature on mechanical properties of Ti-(43-54)Al-xMn-yNb (x=0, 3, 4, y=0, 4) alloys. The compressive yield strength as well as fracture strain was correlated with composition, microstructure, tetragonality, and strain rate. The controlled microstructures obtained by heat treatments were introduced in order to correlate the microstructural parameters with mechanical properties. The variation behavior of compressive yield strength of Ti_(49)Al_(51) base alloys showed the positive temperature dependence and the highest compressive yield strength among the measured six alloys was obtained in (Ti_(49)Al_(51))_(92)Mn₄Nb₄. The c/a ratio of (Ti_(53)Al_(47))_(97)Mn₃ alloy was measured using hot stage in-situ XRD technique at different temperatures. The c/a ratio was decreased significantly at 1273K. The c/a ratio of Ti-(43-54)Al-xMn-yNb (x=0, 3, 4, y=0, 4) base alloys also varied with the compositions. The compressive fracture strain of Ti_(53)Al_(47) base alloys was increased with decrease of the c/a ratio, while Ti_(49)Al_(51) base alloys had no correlation with the c/a ratio.

PST-TiAl 금속간화합물의 변형 및 파괴거동의 이방성 : TEM 직접관찰

표성규,김낙준 대한금속재료학회(대한금속학회) 1998 대한금속·재료학회지 Vol.36 No.9

In-situ straining experiments in the TEM have been performed on thin foils of polysynthetically twinned(PST) crystals of Ti-49.3 at% Al. As expected, the deformation behavior of PST crystals of TiAl is anisotropic, depending on the angle between the lamellar boundaries and tensile loading axis. Shear deformation proceeds, in a zigzag fashion, across the lamellar boundaries when tensile loading axis is parallel to the lamellar boundaries. For tensile loading perpendicular to the lamellar boundaries, deformation occurs across the lamellar boundaries, whereas crack propagates along the lamellar boundaries. When tensile loading axis is inclined at an intermediate angle to the lamellar boundaries, shear deformation occurs parallel to the lamellar boundaries. The α₂ phase plays different roles depending on the orientation. Roles of the various types of interfaces in the locallized deformation and fracture behavior have been evaluated to understand the overall behavior of the PST crystals.

Chemical Bond Structure and MOSFET Device Damages of Electron Beam Cured Siloxane Spin-on-dielectric Films

표성규 대한금속·재료학회 2014 ELECTRONIC MATERIALS LETTERS Vol.10 No.6

This paper presents the properties of electron beam cured SOG (spin-on-glass) films in terms of the chemical bond structure and accompanying device damages. It is observed that e-beam cured SOG films do not show the Si-CH bonds in the FT-IR spectra but still have the carbons in the film which are thermally stable. As for the device damage, the experimental result shows that the threshold voltage of nMOSFET decreases by positive charging of gate oxide after e-beam curing process and it shows antenna ratio independence. Also, the variation of threshold voltage is largely affected by the cathode voltage, which determines the electron energy and interlayer dielectric thickness.

Role of CH₂I₂ Catalysis in Chemically Enhanced MOCVD Cu Process: Nature of Superfilling in Copper Thin Film Growth

표성규 대한금속·재료학회 2008 METALS AND MATERIALS International Vol.14 No.6

This study is concerned with the effect of CH₂I₂ iodine catalysis on the film structure and superfilling properties of Chemically Enhanced Chemical Vapor Deposition (CECVD) Cu process. It was found that, under optimal conditions, treatment of MOCVD Cu deposition with a chemical enhancer increases deposition rate and intensity and decreases the incubation time and surface roughness. These results imply that the chemical enhancer has a surfactant effect that promotes two-dimensional layer-by-layer growth. The deposition of CECVD Cu film in the low temperature region (< 150℃) shows superfilling behavior and void-free filling, but shows conformal step coverage in the intermediate temperature range. The growth of CECVD Cu film does not proceed in a layer-by-layer manner, and becomes agglomerate in the high temperature region (190℃). Superconformal coverage and the best superfilling performance of CEMOCVD Cu film is demonstrated with a (hfac)Cu(DMB) precursor of 0.10 um feature size and 17500A height [AR = 17.5:1]. This study is concerned with the effect of CH₂I₂ iodine catalysis on the film structure and superfilling properties of Chemically Enhanced Chemical Vapor Deposition (CECVD) Cu process. It was found that, under optimal conditions, treatment of MOCVD Cu deposition with a chemical enhancer increases deposition rate and intensity and decreases the incubation time and surface roughness. These results imply that the chemical enhancer has a surfactant effect that promotes two-dimensional layer-by-layer growth. The deposition of CECVD Cu film in the low temperature region (< 150℃) shows superfilling behavior and void-free filling, but shows conformal step coverage in the intermediate temperature range. The growth of CECVD Cu film does not proceed in a layer-by-layer manner, and becomes agglomerate in the high temperature region (190℃). Superconformal coverage and the best superfilling performance of CEMOCVD Cu film is demonstrated with a (hfac)Cu(DMB) precursor of 0.10 um feature size and 17500A height [AR = 17.5:1].

고강도 7075 Al 합금의 가공 열처리와 미세조직의 상관관계연구

표성규,김재중,김낙준 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.8

The main objective of the present investigation is to study the effect of the thermomechanical treatment on the structure-property relationships of 7075 plate. Particular emphasis has been placed on clarifying the origin of the anisotropy of mechanical properties. It shows that the application of thermomechanical treatment improves the microstructure and overall tensile properties of 7075 plate. Grain size becomes finer and the morphology of coarse intermetallic particles become favorable as the 7075 plate is thermomechanically processed. This improvement of microstructure directly influences the tensile properties of 7075 plate. While the thermomechanically treated (TMT) 7075 plate don't show any significant change in tensile properties with specimen orientation, there exists a large variation of tensile properties, in especially elongation, of heat treated (HT) 7075 plate with specimen orientation. HT 7075 plate in LT orientation has a much lower elongation than that in I. orientation. Detailed fractographic study reveals that poor ductility in LT oriented specimen is due to the large effective grain size and also due to the occurrence of cleavage fracture of coarse intermetallic particles along grain boundaries. In short, it has been found that the application of thermomechanical treatment improves the tensile properties of 7075 plate and it can be directly applied for the alloy processing for forged harts.