Cell Wong - Academia.edu (original) (raw)
Papers by Cell Wong
Microelectronics Reliability
Overdriving reliability of chip scale packaged LEDs Quantitatively analyzing the impact of component
IEEE Electron Device Letters, 2016
Using the analogue of the electric inductance, we reveal the properties of the thermal inductance... more Using the analogue of the electric inductance, we reveal the properties of the thermal inductance in GaN-based light-emitting diode (LED) devices by testing their transient thermal behaviours. We find that the devices exhibit a transient thermal response under step-down or step-up currents and observe notable inductive phenomena of the temperature response as time evolves from start up to some hundred microseconds. We define thermal inductance as the rapid change in device temperature that is opposite to the temperature change expected from the power input. These findings can promote new temperature measurements, and novel thermal analyses of high-frequency semiconductor devices that combining the thermal resistances, thermal capacitances, and thermal inductances.
2011 12th Intl. Conf. on Thermal, Mechanical & Multi-Physics Simulation and Experiments in Microelectronics and Microsystems, 2011
The traction-displacement relations of the epoxycopper interfaces are studied using an atomistic ... more The traction-displacement relations of the epoxycopper interfaces are studied using an atomistic model. The reaction force of the epoxy layer in response to displacement of the interface is calculated during molecular dynamics simulation. A parametric study in terms of displacement rate and the step size of displacement increment has been performed. The traction-displacement relations are found sensitive to the step size of the displacement increment. The tractiondisplacement relations are better described with a small displacement increment in the initial region where the epoxy-copper interface is in close contact. The interfacial energy as calculated by the tractiondisplacement model is-0.28 Jm-2 which is comparable to the value obtained from a static model. This calculated value is also close to the thermodynamic work of adhesion (-0.26 Jm-2) of an epoxy-copper system as reported in the literature [1].
2013 10th China International Forum on Solid State Lighting (ChinaSSL), 2013
Scientific reports, Jan 9, 2016
In this paper, we present a first-principles and molecular dynamics study to delineate the functi... more In this paper, we present a first-principles and molecular dynamics study to delineate the functionalization-induced changes in the local structure and the physical properties of amorphous polyaniline. The results of radial distribution function (RDF) demonstrate that introducing -SO3(-)Na(+) groups at phenyl rings leads to the structural changes in both the intrachain and interchain ordering of polyaniline at shorter distances (≤5 Å). An unique RDF feature in 1.8-2.1 Å regions is usually observed in both the interchain and intrachain RDF profiles of the -SO3(-)Na(+) substituted polymer (i.e. Na-SPANI). Comparative studies of the atom-atom pairs, bond structures, torsion angles and three-dimensional structures show that EB-PANI has much better intrachain ordering than that of Na-SPANI. In addition, investigation of the band gap, density of states (DOS), and absorption spectra indicates that the derivatization at ring do not substantially alter the inherent electronic properties but ...
2013 10th China International Forum on Solid State Lighting (ChinaSSL), 2013
IEEE Electron Device Letters, 2015
Molecular Modeling and Multiscaling Issues for Electronic Material Applications, 2014
... The findings suggested that cupric oxide (CuO) which resulted in needle-like morphology playe... more ... The findings suggested that cupric oxide (CuO) which resulted in needle-like morphology played a dominant ... epoxy systems and will help to establish the guidelines in the selection of SAM ... A roughmorphology on one hand can improve adhesion through surface interlocking. ...
Proceedings - Electronic Components and Technology Conference
Interfacial delamination, due to the presence of dissimilar material systems, is one of the prima... more Interfacial delamination, due to the presence of dissimilar material systems, is one of the primary concerns in electronic package design. The mismatch in coefficient of thermal expansion between the different layers in the packages can generate high interfacial stresses due to thermal loading during fabrication and assembly. The present study is focused on the delamination at the Epoxy Molding Compound (EMC)/copper interface. Different EMC materials molded on copper leadframe were tested with different shear height. The stresses at the interface were evaluated using data from the button shear test (BST). Conventional failure criteria are not able to explain the stress results observed from the button shear test data. In this study, a multi-scale model was built to determine the interfacial energy between EMC and copper substrate. The interfacial material properties were evaluated from the interaction energy between EMC and Cu substrate. The interaction of EMC and Cu can be measured using the atomic force microscope (AFM). The force-distance curve obtained directly from AFM measurement is used to determine the interfacial material properties. The properties were input to the multi-scale model. Experimental force from the BST was applied to the model. The interfacial tensile stress and shear stress were evaluated and were used to calculate the interfacial energy. An energy-based failure criterion for delamination was set up. In order to benchmark the delamination failure criterion, two electronic packages, SOT #1 and SOT #2 were studied to investigate delamination in the soldering reflow process. Based on the proposed method, the predicted results were found to be consistent with those from C-SAM measurement.
56th Electronic Components and Technology Conference 2006, 2006
Moisture induced reliability concerns have been extensively studied in package design. Popcorning... more Moisture induced reliability concerns have been extensively studied in package design. Popcorning in plastic-encapsulated IC packages is a defect frequently occurring in solder reflow due to moisture penetration into the packages. Moisture diffusion has a detrimental effect on the epoxy/copper interfacial adhesion and drastically reduces the reliability of the encapsulated package. The present study is focused on the moisture diffusion
Proceedings - Electronic Components and Technology Conference
Reliability of electronic packages is a great concern to packaging design engineers. During its d... more Reliability of electronic packages is a great concern to packaging design engineers. During its design life, packages experience a wide range of temperature variations. The mismatch in coefficient of thermal expansion between the different layers in the packages can generate high interfacial stresses due to these thermal loading. If these stresses exceed the limiting value, delamination will occur. The present study is focused on the reliability of the epoxy molding compound (EMC) and cuprous oxide coated copper substrate. In order to verify whether the interfacial adhesion is dominant by the content of cuprous oxide on the cooper substrate, two models were built to simulate the thermal cycling test with a constant cuprous oxide and a changing content of cuprous oxide on the copper substrate. The thermal cycling test was conducted with a given thermal profile. The adhesion strength between EMC and cuprous oxide coated copper substrate at different thermal cycles was evaluated using the button shear test (BST). A simple molecular model of a bi-material system, which consists of EMC and cuprous oxide coated copper substrate, was built to evaluate the interfacial energy of the Cu-EMC system. In order to dramatically reduce the computational time, the system was modeled with a limited number of atoms. A preset strain was applied to the model representing a forcing step as the EMC material was pulled away from the copper substrate. Equilibration was conducted to relax the whole system before the next strain step proceeded. The procedure was repeated using different strains. The interfacial energy at different thermal cycles was evaluated. The variation of the interfacial energy indicated the change in the adhesion strength between EMC and cuprous oxide coated copper during the thermal cycling test. The simulation results revealed that the cuprous oxide content in the copper substrate had a large effect on the adhesion between EMC and copper, which is consistent with the experimental observation.
We propose a molecular modeling strategy, which is capable of predicting the conductivity change ... more We propose a molecular modeling strategy, which is capable of predicting the conductivity change of emeraldine base polyaniline polymer due to different degree of protonic acid doping. The method is comprised of two key steps: (1) generating the amorphous unit cells with given number of polymer molecules and different concentration of H+ ions by Monte Carlo algorithm; (2) modeling the doping chemical reaction by using a scripted loop control molecular mechanics/molecular dynamics simulation. This modeling strategy can be used for optimal/robust selection and design of conductive polymers for various applications.
Molecular Modeling and Multiscaling Issues for Electronic Material Applications, 2014
This paper describes a methodology in predicting color of the LED packages in different phosphor ... more This paper describes a methodology in predicting color of the LED packages in different phosphor geometry for package free LED. Through resolving the peaks attributed from the LED and phosphor, the Phosphor Spectral Portion-Vol. ratio relations was developed. From the relations, the spectrum for a LED with known phosphor geometry can be constructed. Color of the LED can then be deduced. The method serves the geometric design of the phosphor layer for package free LEDs.
Journal of Semiconductors
Chip on flexible substrate (COF) is a new packaging technology for light emitting diodes (LED). T... more Chip on flexible substrate (COF) is a new packaging technology for light emitting diodes (LED). This paper investigated the effect of Cu-pillar in the polyimide (PI) layer on the thermal properties of COF LED packages by finite element analysis. The thermal distribution and thermal resistance were studied in both COF LED packages with and without Cu-pillar. The PI layer showed the highest thermal resistance in the typical package and led to a high chip temperature. With the addition of Cu-pillars, however, the thermal resistance of the PI layer significantly decreased due to the improvement of vertical thermal dissipation under LED chips. Based on the results of simulation and calculation, the relationship between the amount of Cu-pillar and thermal resistance of the COF package has been built. For the packages studied in this research, an 8 × 8 Cu-pillars array was adequate to improve the thermal performance of COF packages.
Proceedings Electronic Components and Technology, 2005. ECTC '05., 2005
Polymer flip chip process utilizes Ag filled thermoset and/or thermoplastic polymers, in combinat... more Polymer flip chip process utilizes Ag filled thermoset and/or thermoplastic polymers, in combination with stencil printing processes to form polymer bump interconnects of flip chip I.C. devices [1]. Nevertheless, slumping behavior of conventional polymer interconnect material during bumping process on the wafer chip has constrained the bump height achieved by the most common stencil printing to 50µm [2]. A bumping process to form fine pitch, high aspect ratio polymer flip chip bumps without slumping was developed by producing a through-hole PDMS micro-transfer mould on a metallized wafer [3]. In this paper, a MEMS chip [4] was packaged by the PDMS micro-transfer mould technique to evaluate the performance of the interconnection method. Flip chip assembly process was then performed on the printed circuit board (PCB) and some functionality tests was conducted afterwards. The designed dimension of the polymer bump is 150µm in diameter, 90µm in height, and at a 245µm pitch. Bump adhesion force was measured and found to be about 40gram. Electrical conductivity test was also conducted after PCB assembly as preliminary reliability test of the whole assembly process. Results showed that the MEMS chip was functioning well with new polymer bumping method. With this bumping approach, intrinsic slumping problem of the conductive polymer paste is resolved. This low temperature fabrication technique is an important development for MEMS packaging.
2010 11th International Thermal, Mechanical & Multi-Physics Simulation, and Experiments in Microelectronics and Microsystems (EuroSimE), 2010
Despite the fact that epoxy has continuously used as encapsulant in electronic packaging, its joi... more Despite the fact that epoxy has continuously used as encapsulant in electronic packaging, its joint with copper-based substrate is prone to delaminate during reliability test. A prime reason is the lack of adhesion between Cu and epoxy compound. To solve the problem, self-assembly molecular structure (SAM) is adopted to improve adhesion of epoxy-copper system. In seeing that hydrophobic behaviour of the SAM structure may hinder moisture diffusion along the interface, further work in terms of the molecular structure of the SAM candidates is conducted in this study. This work aims at investigating the moisture effect on the interfacial adhesion with different types of SAM modified interfaces through molecular dynamic (MD) simulations. This study uses MD model as a tool to 1) predict the interfacial adhesion of the SAM modified interface in moisture sensitive condition; 2) investigate the moisture diffusion behavior of the modified interfaces under moisture sensitive conditions. The results demonstrate a reasonable qualitative corelation between the MD prediction and the TDCB tested data. Nevertheless, without the experimental adsorption data for the SAM material, the moisture diffusion coefficient obtained from MD study cannot explain the adhesion degradation after aging.
56th Electronic Components and Technology Conference 2006, 2006
This paper presents a novel nano-scale interfacial covalent bond measurement method by atomic for... more This paper presents a novel nano-scale interfacial covalent bond measurement method by atomic force microscopy (AFM) with reference to the adhesion of self-assembly monolayer on epoxy/copper systems. Covalent bond strength measurements were conducted using AFM for self assembly monolayer (SAM) coated copper (Cu) tips on epoxy after epoxy has been cured at its curing temperature. In-situ curing of Cu-epoxy force
2006 Thirty-First IEEE/CPMT International Electronics Manufacturing Technology Symposium, 2006
This paper presents a study of disulfide thin film onto sputtered Cu substrate. Extrinsic paramet... more This paper presents a study of disulfide thin film onto sputtered Cu substrate. Extrinsic parameter includes solution concentration, deposition time and agitation has been investigated. Ellipsometer was used to measure the molecular film thickness. It has been discovered that agitation which prevents local concentration of disulfide solution, is crucial for success of film deposition. Without agitation, larger thickness variation has been attained (36±22A comparing with 30±16A). Furthermore, relatively uniform film (37±10A for DS-A, 30±8A for DS-C) can be realized from low concentration (0.5gtM) ethanol in lhr. No significant aggregates but few pinholes have been found on disulfide treated surface. An experiment procedure in obtaining uniform thin film from disulfide solution on Cu substrate has been investigated.
Microelectronics Reliability
Overdriving reliability of chip scale packaged LEDs Quantitatively analyzing the impact of component
IEEE Electron Device Letters, 2016
Using the analogue of the electric inductance, we reveal the properties of the thermal inductance... more Using the analogue of the electric inductance, we reveal the properties of the thermal inductance in GaN-based light-emitting diode (LED) devices by testing their transient thermal behaviours. We find that the devices exhibit a transient thermal response under step-down or step-up currents and observe notable inductive phenomena of the temperature response as time evolves from start up to some hundred microseconds. We define thermal inductance as the rapid change in device temperature that is opposite to the temperature change expected from the power input. These findings can promote new temperature measurements, and novel thermal analyses of high-frequency semiconductor devices that combining the thermal resistances, thermal capacitances, and thermal inductances.
2011 12th Intl. Conf. on Thermal, Mechanical & Multi-Physics Simulation and Experiments in Microelectronics and Microsystems, 2011
The traction-displacement relations of the epoxycopper interfaces are studied using an atomistic ... more The traction-displacement relations of the epoxycopper interfaces are studied using an atomistic model. The reaction force of the epoxy layer in response to displacement of the interface is calculated during molecular dynamics simulation. A parametric study in terms of displacement rate and the step size of displacement increment has been performed. The traction-displacement relations are found sensitive to the step size of the displacement increment. The tractiondisplacement relations are better described with a small displacement increment in the initial region where the epoxy-copper interface is in close contact. The interfacial energy as calculated by the tractiondisplacement model is-0.28 Jm-2 which is comparable to the value obtained from a static model. This calculated value is also close to the thermodynamic work of adhesion (-0.26 Jm-2) of an epoxy-copper system as reported in the literature [1].
2013 10th China International Forum on Solid State Lighting (ChinaSSL), 2013
Scientific reports, Jan 9, 2016
In this paper, we present a first-principles and molecular dynamics study to delineate the functi... more In this paper, we present a first-principles and molecular dynamics study to delineate the functionalization-induced changes in the local structure and the physical properties of amorphous polyaniline. The results of radial distribution function (RDF) demonstrate that introducing -SO3(-)Na(+) groups at phenyl rings leads to the structural changes in both the intrachain and interchain ordering of polyaniline at shorter distances (≤5 Å). An unique RDF feature in 1.8-2.1 Å regions is usually observed in both the interchain and intrachain RDF profiles of the -SO3(-)Na(+) substituted polymer (i.e. Na-SPANI). Comparative studies of the atom-atom pairs, bond structures, torsion angles and three-dimensional structures show that EB-PANI has much better intrachain ordering than that of Na-SPANI. In addition, investigation of the band gap, density of states (DOS), and absorption spectra indicates that the derivatization at ring do not substantially alter the inherent electronic properties but ...
2013 10th China International Forum on Solid State Lighting (ChinaSSL), 2013
IEEE Electron Device Letters, 2015
Molecular Modeling and Multiscaling Issues for Electronic Material Applications, 2014
... The findings suggested that cupric oxide (CuO) which resulted in needle-like morphology playe... more ... The findings suggested that cupric oxide (CuO) which resulted in needle-like morphology played a dominant ... epoxy systems and will help to establish the guidelines in the selection of SAM ... A roughmorphology on one hand can improve adhesion through surface interlocking. ...
Proceedings - Electronic Components and Technology Conference
Interfacial delamination, due to the presence of dissimilar material systems, is one of the prima... more Interfacial delamination, due to the presence of dissimilar material systems, is one of the primary concerns in electronic package design. The mismatch in coefficient of thermal expansion between the different layers in the packages can generate high interfacial stresses due to thermal loading during fabrication and assembly. The present study is focused on the delamination at the Epoxy Molding Compound (EMC)/copper interface. Different EMC materials molded on copper leadframe were tested with different shear height. The stresses at the interface were evaluated using data from the button shear test (BST). Conventional failure criteria are not able to explain the stress results observed from the button shear test data. In this study, a multi-scale model was built to determine the interfacial energy between EMC and copper substrate. The interfacial material properties were evaluated from the interaction energy between EMC and Cu substrate. The interaction of EMC and Cu can be measured using the atomic force microscope (AFM). The force-distance curve obtained directly from AFM measurement is used to determine the interfacial material properties. The properties were input to the multi-scale model. Experimental force from the BST was applied to the model. The interfacial tensile stress and shear stress were evaluated and were used to calculate the interfacial energy. An energy-based failure criterion for delamination was set up. In order to benchmark the delamination failure criterion, two electronic packages, SOT #1 and SOT #2 were studied to investigate delamination in the soldering reflow process. Based on the proposed method, the predicted results were found to be consistent with those from C-SAM measurement.
56th Electronic Components and Technology Conference 2006, 2006
Moisture induced reliability concerns have been extensively studied in package design. Popcorning... more Moisture induced reliability concerns have been extensively studied in package design. Popcorning in plastic-encapsulated IC packages is a defect frequently occurring in solder reflow due to moisture penetration into the packages. Moisture diffusion has a detrimental effect on the epoxy/copper interfacial adhesion and drastically reduces the reliability of the encapsulated package. The present study is focused on the moisture diffusion
Proceedings - Electronic Components and Technology Conference
Reliability of electronic packages is a great concern to packaging design engineers. During its d... more Reliability of electronic packages is a great concern to packaging design engineers. During its design life, packages experience a wide range of temperature variations. The mismatch in coefficient of thermal expansion between the different layers in the packages can generate high interfacial stresses due to these thermal loading. If these stresses exceed the limiting value, delamination will occur. The present study is focused on the reliability of the epoxy molding compound (EMC) and cuprous oxide coated copper substrate. In order to verify whether the interfacial adhesion is dominant by the content of cuprous oxide on the cooper substrate, two models were built to simulate the thermal cycling test with a constant cuprous oxide and a changing content of cuprous oxide on the copper substrate. The thermal cycling test was conducted with a given thermal profile. The adhesion strength between EMC and cuprous oxide coated copper substrate at different thermal cycles was evaluated using the button shear test (BST). A simple molecular model of a bi-material system, which consists of EMC and cuprous oxide coated copper substrate, was built to evaluate the interfacial energy of the Cu-EMC system. In order to dramatically reduce the computational time, the system was modeled with a limited number of atoms. A preset strain was applied to the model representing a forcing step as the EMC material was pulled away from the copper substrate. Equilibration was conducted to relax the whole system before the next strain step proceeded. The procedure was repeated using different strains. The interfacial energy at different thermal cycles was evaluated. The variation of the interfacial energy indicated the change in the adhesion strength between EMC and cuprous oxide coated copper during the thermal cycling test. The simulation results revealed that the cuprous oxide content in the copper substrate had a large effect on the adhesion between EMC and copper, which is consistent with the experimental observation.
We propose a molecular modeling strategy, which is capable of predicting the conductivity change ... more We propose a molecular modeling strategy, which is capable of predicting the conductivity change of emeraldine base polyaniline polymer due to different degree of protonic acid doping. The method is comprised of two key steps: (1) generating the amorphous unit cells with given number of polymer molecules and different concentration of H+ ions by Monte Carlo algorithm; (2) modeling the doping chemical reaction by using a scripted loop control molecular mechanics/molecular dynamics simulation. This modeling strategy can be used for optimal/robust selection and design of conductive polymers for various applications.
Molecular Modeling and Multiscaling Issues for Electronic Material Applications, 2014
This paper describes a methodology in predicting color of the LED packages in different phosphor ... more This paper describes a methodology in predicting color of the LED packages in different phosphor geometry for package free LED. Through resolving the peaks attributed from the LED and phosphor, the Phosphor Spectral Portion-Vol. ratio relations was developed. From the relations, the spectrum for a LED with known phosphor geometry can be constructed. Color of the LED can then be deduced. The method serves the geometric design of the phosphor layer for package free LEDs.
Journal of Semiconductors
Chip on flexible substrate (COF) is a new packaging technology for light emitting diodes (LED). T... more Chip on flexible substrate (COF) is a new packaging technology for light emitting diodes (LED). This paper investigated the effect of Cu-pillar in the polyimide (PI) layer on the thermal properties of COF LED packages by finite element analysis. The thermal distribution and thermal resistance were studied in both COF LED packages with and without Cu-pillar. The PI layer showed the highest thermal resistance in the typical package and led to a high chip temperature. With the addition of Cu-pillars, however, the thermal resistance of the PI layer significantly decreased due to the improvement of vertical thermal dissipation under LED chips. Based on the results of simulation and calculation, the relationship between the amount of Cu-pillar and thermal resistance of the COF package has been built. For the packages studied in this research, an 8 × 8 Cu-pillars array was adequate to improve the thermal performance of COF packages.
Proceedings Electronic Components and Technology, 2005. ECTC '05., 2005
Polymer flip chip process utilizes Ag filled thermoset and/or thermoplastic polymers, in combinat... more Polymer flip chip process utilizes Ag filled thermoset and/or thermoplastic polymers, in combination with stencil printing processes to form polymer bump interconnects of flip chip I.C. devices [1]. Nevertheless, slumping behavior of conventional polymer interconnect material during bumping process on the wafer chip has constrained the bump height achieved by the most common stencil printing to 50µm [2]. A bumping process to form fine pitch, high aspect ratio polymer flip chip bumps without slumping was developed by producing a through-hole PDMS micro-transfer mould on a metallized wafer [3]. In this paper, a MEMS chip [4] was packaged by the PDMS micro-transfer mould technique to evaluate the performance of the interconnection method. Flip chip assembly process was then performed on the printed circuit board (PCB) and some functionality tests was conducted afterwards. The designed dimension of the polymer bump is 150µm in diameter, 90µm in height, and at a 245µm pitch. Bump adhesion force was measured and found to be about 40gram. Electrical conductivity test was also conducted after PCB assembly as preliminary reliability test of the whole assembly process. Results showed that the MEMS chip was functioning well with new polymer bumping method. With this bumping approach, intrinsic slumping problem of the conductive polymer paste is resolved. This low temperature fabrication technique is an important development for MEMS packaging.
2010 11th International Thermal, Mechanical & Multi-Physics Simulation, and Experiments in Microelectronics and Microsystems (EuroSimE), 2010
Despite the fact that epoxy has continuously used as encapsulant in electronic packaging, its joi... more Despite the fact that epoxy has continuously used as encapsulant in electronic packaging, its joint with copper-based substrate is prone to delaminate during reliability test. A prime reason is the lack of adhesion between Cu and epoxy compound. To solve the problem, self-assembly molecular structure (SAM) is adopted to improve adhesion of epoxy-copper system. In seeing that hydrophobic behaviour of the SAM structure may hinder moisture diffusion along the interface, further work in terms of the molecular structure of the SAM candidates is conducted in this study. This work aims at investigating the moisture effect on the interfacial adhesion with different types of SAM modified interfaces through molecular dynamic (MD) simulations. This study uses MD model as a tool to 1) predict the interfacial adhesion of the SAM modified interface in moisture sensitive condition; 2) investigate the moisture diffusion behavior of the modified interfaces under moisture sensitive conditions. The results demonstrate a reasonable qualitative corelation between the MD prediction and the TDCB tested data. Nevertheless, without the experimental adsorption data for the SAM material, the moisture diffusion coefficient obtained from MD study cannot explain the adhesion degradation after aging.
56th Electronic Components and Technology Conference 2006, 2006
This paper presents a novel nano-scale interfacial covalent bond measurement method by atomic for... more This paper presents a novel nano-scale interfacial covalent bond measurement method by atomic force microscopy (AFM) with reference to the adhesion of self-assembly monolayer on epoxy/copper systems. Covalent bond strength measurements were conducted using AFM for self assembly monolayer (SAM) coated copper (Cu) tips on epoxy after epoxy has been cured at its curing temperature. In-situ curing of Cu-epoxy force
2006 Thirty-First IEEE/CPMT International Electronics Manufacturing Technology Symposium, 2006
This paper presents a study of disulfide thin film onto sputtered Cu substrate. Extrinsic paramet... more This paper presents a study of disulfide thin film onto sputtered Cu substrate. Extrinsic parameter includes solution concentration, deposition time and agitation has been investigated. Ellipsometer was used to measure the molecular film thickness. It has been discovered that agitation which prevents local concentration of disulfide solution, is crucial for success of film deposition. Without agitation, larger thickness variation has been attained (36±22A comparing with 30±16A). Furthermore, relatively uniform film (37±10A for DS-A, 30±8A for DS-C) can be realized from low concentration (0.5gtM) ethanol in lhr. No significant aggregates but few pinholes have been found on disulfide treated surface. An experiment procedure in obtaining uniform thin film from disulfide solution on Cu substrate has been investigated.