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Shiv Govind Singh - One of the best experts on this subject based on the ideXlab platform.
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Diffusion Enhanced Drive Sub 100 °C Wafer Level Fine-Pitch Cu-Cu Thermocompression Bonding for 3D IC Integration
2019 IEEE 69th Electronic Components and Technology Conference (ECTC), 2019Co-Authors: Asisa Kumar Panigrahy, Siva Rama Krishna Vanjari, Tamal Ghosh, Satish Bonam, Shiv Govind SinghAbstract:One of the primary and critical requirements for high quality wafer level Thermocompression Copper-Copper (Cu-Cu) bonding is the fast diffusion of Cu atoms across the boundary between two bonding layers. In this paper, we demonstrate low temperature, low pressure and fine pitch Cu-Cu Thermocompression bonding by enhancing intrinsic diffusivity at the bonding interface by stress gradient. Stress in the Cu surface was fixed up by simply varying the Ar pressure during physical deposition using the sputtering tool and observed clearly that one of the other deposited wafers had opposite stress and highest differential stress not only led to fine-pitch bonding at sub 100°C with very low external pressure of 0.25 MPa. Retention of stress even in the smaller patterns was clearly observed using conventional non-destructive wafer bow technique and further corroborated using solid mechanic module of COMSOL Multiphysics simulator. The quality of stress engineered fine-pitch bonded sample was examined using the pull test and Idonus Wafer Bonder IR Inspection (WBI) tool. Furthermore, the absence of voids and defect free bonding interface clearly opens up realistic chances for three dimensional (3D) IC integration. Moreover, this novel stress tailoring Cu surface modification prior to bonding is the primary contestant for future heterogeneous integration.
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Interface and Reliability Analysis of Au-Passivated Cu–Cu Fine-Pitch Thermocompression Bonding for 3-D IC Applications
IEEE Transactions on Components Packaging and Manufacturing Technology, 2019Co-Authors: Satish Bonam, C. Hemanth Kumar, Siva Rama Krishna Vanjari, Asisa Kumar Panigrahi, Shiv Govind SinghAbstract:Optimally engineered ultrathin gold (Au) layer as an effective surface passivation for low-temperature, low-pressure fine-pitch Cu–Cu bonding is demonstrated in this paper. The Au passivation layer not only performs the role of protecting the underlying Cu surface from unwanted oxidation but it also helps in reducing the effective surface roughness, which are two major requirements for Thermocompression bonding. In addition, Au, being a noble metal, ensures efficient surface passivation of Cu even at elevated temperatures. Furthermore, Au-passivated Cu surfaces show significantly high {111}-oriented surface planes with random grain structures at the bonding interface, which account for enhanced diffusion ability. Herein, an optimized Au passivation layer of 3 nm has resulted in high-quality fine-pitch Cu–Cu Thermocompression bonding at 140 °C and 0.3-MPa pressure. The bonded samples have further been subjected to various reliability studies in order to confirm the efficacy of the proposed bonding scheme, along with mathematical modeling to cross check using Fick’s second law of approximation. The bonded samples have attributed to a high bond strength (>200 MPa) and a very low and stable specific contact resistance ( $\sim 1.43 \times 10^{\mathrm {-8}}\Omega $ cm $^{2}$ ) under robust conditions, which is significantly better than the values previously reported in the literature.
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Direct, CMOS In-Line Process Flow Compatible, Sub 100 °C Cu–Cu Thermocompression Bonding Using Stress Engineering
Electronic Materials Letters, 2018Co-Authors: Asisa Kumar Panigrahi, C. Hemanth Kumar, Shiv Govind Singh, Tamal Ghosh, Siva Rama Krishna VanjariAbstract:Diffusion of atoms across the boundary between two bonding layers is the key for achieving excellent Thermocompression Wafer on Wafer bonding. In this paper, we demonstrate a novel mechanism to increase the diffusion across the bonding interface and also shows the CMOS in-line process flow compatible Sub 100 °C Cu–Cu bonding which is devoid of Cu surface treatment prior to bonding. The stress in sputtered Cu thin films was engineered by adjusting the Argon in-let pressure in such a way that one film had a compressive stress while the other film had tensile stress. Due to this stress gradient, a nominal pressure (2 kN) and temperature (75 °C) was enough to achieve a good quality Thermocompression bonding having a bond strength of 149 MPa and very low specific contact resistance of 1.5 × 10^−8 Ω-cm^2. These excellent mechanical and electrical properties are resultant of a high quality Cu–Cu bonding having grain growth between the Cu films across the boundary and extended throughout the bonded region as revealed by Cross-sectional Transmission Electron Microscopy. In addition, reliability assessment of Cu–Cu bonding with stress engineering was demonstrated using multiple current stressing and temperature cycling test, suggests excellent reliable bonding without electrical performance degradation.
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direct cmos in line process flow compatible sub 100 c cu cu Thermocompression bonding using stress engineering
Electronic Materials Letters, 2018Co-Authors: Asisa Kumar Panigrahi, Shiv Govind Singh, Tamal Ghosh, Hemanth C Kumar, Siva Rama Krishna VanjariAbstract:Diffusion of atoms across the boundary between two bonding layers is the key for achieving excellent Thermocompression Wafer on Wafer bonding. In this paper, we demonstrate a novel mechanism to increase the diffusion across the bonding interface and also shows the CMOS in-line process flow compatible Sub 100 °C Cu–Cu bonding which is devoid of Cu surface treatment prior to bonding. The stress in sputtered Cu thin films was engineered by adjusting the Argon in-let pressure in such a way that one film had a compressive stress while the other film had tensile stress. Due to this stress gradient, a nominal pressure (2 kN) and temperature (75 °C) was enough to achieve a good quality Thermocompression bonding having a bond strength of 149 MPa and very low specific contact resistance of 1.5 × 10−8 Ω-cm2. These excellent mechanical and electrical properties are resultant of a high quality Cu–Cu bonding having grain growth between the Cu films across the boundary and extended throughout the bonded region as revealed by Cross-sectional Transmission Electron Microscopy. In addition, reliability assessment of Cu–Cu bonding with stress engineering was demonstrated using multiple current stressing and temperature cycling test, suggests excellent reliable bonding without electrical performance degradation.
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WoW Post-CMOS compatible Cu-Cu Low temperature, Low pressure Thermocompression bonding with Pd passivation Engineering
2017Co-Authors: C. Hemanth Kumar, Siva Rama Krishna Vanjari, Shiv Govind SinghAbstract:Surface passivation of Copper plays vital role in accomplishing low temperature, low pressure Wafer-on-Wafer (WoW) Cu-Cu Thermocompression bonding, as it not only helps in protecting the Cu surface from oxidation but also smoothen the surface. Ultra-thin Palladium (Pd) layer is regarded as one of the promising passivation layer which can prevent oxidation of copper and in addition it can also minimize the roughness of Cu surface. The thickness of Pd layer plays an important role in achieving good and reliable bonding. In this endeavor, we have optimized the Pd passivation thickness to achieve low temperature (150 ˚C) and low pressure (4 bar) WoW Cu-Cu Thermocompression bonding. The optimum thickness of Pd for achieving a good bonding is found out to be 3 nm. Our optimized result yielded an excellent bond interface confirms the reliability of Cu-Cu bonding with Pd passivation.
Siva Rama Krishna Vanjari - One of the best experts on this subject based on the ideXlab platform.
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Diffusion Enhanced Drive Sub 100 °C Wafer Level Fine-Pitch Cu-Cu Thermocompression Bonding for 3D IC Integration
2019 IEEE 69th Electronic Components and Technology Conference (ECTC), 2019Co-Authors: Asisa Kumar Panigrahy, Siva Rama Krishna Vanjari, Tamal Ghosh, Satish Bonam, Shiv Govind SinghAbstract:One of the primary and critical requirements for high quality wafer level Thermocompression Copper-Copper (Cu-Cu) bonding is the fast diffusion of Cu atoms across the boundary between two bonding layers. In this paper, we demonstrate low temperature, low pressure and fine pitch Cu-Cu Thermocompression bonding by enhancing intrinsic diffusivity at the bonding interface by stress gradient. Stress in the Cu surface was fixed up by simply varying the Ar pressure during physical deposition using the sputtering tool and observed clearly that one of the other deposited wafers had opposite stress and highest differential stress not only led to fine-pitch bonding at sub 100°C with very low external pressure of 0.25 MPa. Retention of stress even in the smaller patterns was clearly observed using conventional non-destructive wafer bow technique and further corroborated using solid mechanic module of COMSOL Multiphysics simulator. The quality of stress engineered fine-pitch bonded sample was examined using the pull test and Idonus Wafer Bonder IR Inspection (WBI) tool. Furthermore, the absence of voids and defect free bonding interface clearly opens up realistic chances for three dimensional (3D) IC integration. Moreover, this novel stress tailoring Cu surface modification prior to bonding is the primary contestant for future heterogeneous integration.
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Interface and Reliability Analysis of Au-Passivated Cu–Cu Fine-Pitch Thermocompression Bonding for 3-D IC Applications
IEEE Transactions on Components Packaging and Manufacturing Technology, 2019Co-Authors: Satish Bonam, C. Hemanth Kumar, Siva Rama Krishna Vanjari, Asisa Kumar Panigrahi, Shiv Govind SinghAbstract:Optimally engineered ultrathin gold (Au) layer as an effective surface passivation for low-temperature, low-pressure fine-pitch Cu–Cu bonding is demonstrated in this paper. The Au passivation layer not only performs the role of protecting the underlying Cu surface from unwanted oxidation but it also helps in reducing the effective surface roughness, which are two major requirements for Thermocompression bonding. In addition, Au, being a noble metal, ensures efficient surface passivation of Cu even at elevated temperatures. Furthermore, Au-passivated Cu surfaces show significantly high {111}-oriented surface planes with random grain structures at the bonding interface, which account for enhanced diffusion ability. Herein, an optimized Au passivation layer of 3 nm has resulted in high-quality fine-pitch Cu–Cu Thermocompression bonding at 140 °C and 0.3-MPa pressure. The bonded samples have further been subjected to various reliability studies in order to confirm the efficacy of the proposed bonding scheme, along with mathematical modeling to cross check using Fick’s second law of approximation. The bonded samples have attributed to a high bond strength (>200 MPa) and a very low and stable specific contact resistance ( $\sim 1.43 \times 10^{\mathrm {-8}}\Omega $ cm $^{2}$ ) under robust conditions, which is significantly better than the values previously reported in the literature.
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Direct, CMOS In-Line Process Flow Compatible, Sub 100 °C Cu–Cu Thermocompression Bonding Using Stress Engineering
Electronic Materials Letters, 2018Co-Authors: Asisa Kumar Panigrahi, C. Hemanth Kumar, Shiv Govind Singh, Tamal Ghosh, Siva Rama Krishna VanjariAbstract:Diffusion of atoms across the boundary between two bonding layers is the key for achieving excellent Thermocompression Wafer on Wafer bonding. In this paper, we demonstrate a novel mechanism to increase the diffusion across the bonding interface and also shows the CMOS in-line process flow compatible Sub 100 °C Cu–Cu bonding which is devoid of Cu surface treatment prior to bonding. The stress in sputtered Cu thin films was engineered by adjusting the Argon in-let pressure in such a way that one film had a compressive stress while the other film had tensile stress. Due to this stress gradient, a nominal pressure (2 kN) and temperature (75 °C) was enough to achieve a good quality Thermocompression bonding having a bond strength of 149 MPa and very low specific contact resistance of 1.5 × 10^−8 Ω-cm^2. These excellent mechanical and electrical properties are resultant of a high quality Cu–Cu bonding having grain growth between the Cu films across the boundary and extended throughout the bonded region as revealed by Cross-sectional Transmission Electron Microscopy. In addition, reliability assessment of Cu–Cu bonding with stress engineering was demonstrated using multiple current stressing and temperature cycling test, suggests excellent reliable bonding without electrical performance degradation.
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direct cmos in line process flow compatible sub 100 c cu cu Thermocompression bonding using stress engineering
Electronic Materials Letters, 2018Co-Authors: Asisa Kumar Panigrahi, Shiv Govind Singh, Tamal Ghosh, Hemanth C Kumar, Siva Rama Krishna VanjariAbstract:Diffusion of atoms across the boundary between two bonding layers is the key for achieving excellent Thermocompression Wafer on Wafer bonding. In this paper, we demonstrate a novel mechanism to increase the diffusion across the bonding interface and also shows the CMOS in-line process flow compatible Sub 100 °C Cu–Cu bonding which is devoid of Cu surface treatment prior to bonding. The stress in sputtered Cu thin films was engineered by adjusting the Argon in-let pressure in such a way that one film had a compressive stress while the other film had tensile stress. Due to this stress gradient, a nominal pressure (2 kN) and temperature (75 °C) was enough to achieve a good quality Thermocompression bonding having a bond strength of 149 MPa and very low specific contact resistance of 1.5 × 10−8 Ω-cm2. These excellent mechanical and electrical properties are resultant of a high quality Cu–Cu bonding having grain growth between the Cu films across the boundary and extended throughout the bonded region as revealed by Cross-sectional Transmission Electron Microscopy. In addition, reliability assessment of Cu–Cu bonding with stress engineering was demonstrated using multiple current stressing and temperature cycling test, suggests excellent reliable bonding without electrical performance degradation.
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WoW Post-CMOS compatible Cu-Cu Low temperature, Low pressure Thermocompression bonding with Pd passivation Engineering
2017Co-Authors: C. Hemanth Kumar, Siva Rama Krishna Vanjari, Shiv Govind SinghAbstract:Surface passivation of Copper plays vital role in accomplishing low temperature, low pressure Wafer-on-Wafer (WoW) Cu-Cu Thermocompression bonding, as it not only helps in protecting the Cu surface from oxidation but also smoothen the surface. Ultra-thin Palladium (Pd) layer is regarded as one of the promising passivation layer which can prevent oxidation of copper and in addition it can also minimize the roughness of Cu surface. The thickness of Pd layer plays an important role in achieving good and reliable bonding. In this endeavor, we have optimized the Pd passivation thickness to achieve low temperature (150 ˚C) and low pressure (4 bar) WoW Cu-Cu Thermocompression bonding. The optimum thickness of Pd for achieving a good bonding is found out to be 3 nm. Our optimized result yielded an excellent bond interface confirms the reliability of Cu-Cu bonding with Pd passivation.
J L Reno - One of the best experts on this subject based on the ideXlab platform.
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operation of terahertz quantum cascade lasers at 164 k in pulsed mode and at 117 k in continuous wave mode
Optics Express, 2005Co-Authors: Benjamin S Williams, Sushil Kumar, Qing Hu, J L RenoAbstract:We report the demonstration of a terahertz quantum-cascade laser that operates up to 164 K in pulsed mode and 117 K in continuous-wave mode at approximately 3.0 THz. The active region was based on a resonant-phonon depopulation scheme and a metal-metal waveguide was used for modal confinement. Copper to copper Thermocompression wafer bonding was used to fabricate the waveguide, which displayed improved thermal properties compared to a previous indium-gold bonding method.
C D Richards - One of the best experts on this subject based on the ideXlab platform.
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evaluation of a thermal interface material fabricated using Thermocompression bonding of carbon nanotube turf
Nanotechnology, 2010Co-Authors: A Hamdan, Jeong Hyun Cho, R Johnson, Jun Jiao, D F Bahr, R F Richards, C D RichardsAbstract:In this work a thermal interface material fabricated by Thermocompression bonding of vertically aligned carbon nanotube turf (VACNT) to metallized substrates was characterized. The VACNT structure was fabricated onto silicon substrates using chemical vapor deposition. The structures were then transferred to metallized substrates using Thermocompression bonding. The resulting structure consisted of VACNT turf sandwiched between two layers of Au. Two configurations of VACNT, full coverage and patterned, were fabricated and tested. In addition, the thermal interface resistance of structures at intermediate steps in the Thermocompression bonding process were measured. For the full coverage turf a thermal interface resistance of 1.082 cm2 °C W−1 at an applied load of 1 N was measured, while a thermal interface resistance of 0.044 cm2 °C W−1 at a load of 1 N was measured for the patterned turf configuration.
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Evaluation of a thermal interface material fabricated using Thermocompression bonding of carbon nanotube turf.
Nanotechnology, 2009Co-Authors: A Hamdan, Jeong Hyun Cho, Jun Jiao, D F Bahr, R F Richards, Ryan D. Johnson, C D RichardsAbstract:In this work a thermal interface material fabricated by Thermocompression bonding of vertically aligned carbon nanotube turf (VACNT) to metallized substrates was characterized. The VACNT structure was fabricated onto silicon substrates using chemical vapor deposition. The structures were then transferred to metallized substrates using Thermocompression bonding. The resulting structure consisted of VACNT turf sandwiched between two layers of Au. Two configurations of VACNT, full coverage and patterned, were fabricated and tested. In addition, the thermal interface resistance of structures at intermediate steps in the Thermocompression bonding process were measured. For the full coverage turf a thermal interface resistance of 1.082 cm(2) degrees C W(-1) at an applied load of 1 N was measured, while a thermal interface resistance of 0.044 cm(2) degrees C W(-1) at a load of 1 N was measured for the patterned turf configuration.
Tamal Ghosh - One of the best experts on this subject based on the ideXlab platform.
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Diffusion Enhanced Drive Sub 100 °C Wafer Level Fine-Pitch Cu-Cu Thermocompression Bonding for 3D IC Integration
2019 IEEE 69th Electronic Components and Technology Conference (ECTC), 2019Co-Authors: Asisa Kumar Panigrahy, Siva Rama Krishna Vanjari, Tamal Ghosh, Satish Bonam, Shiv Govind SinghAbstract:One of the primary and critical requirements for high quality wafer level Thermocompression Copper-Copper (Cu-Cu) bonding is the fast diffusion of Cu atoms across the boundary between two bonding layers. In this paper, we demonstrate low temperature, low pressure and fine pitch Cu-Cu Thermocompression bonding by enhancing intrinsic diffusivity at the bonding interface by stress gradient. Stress in the Cu surface was fixed up by simply varying the Ar pressure during physical deposition using the sputtering tool and observed clearly that one of the other deposited wafers had opposite stress and highest differential stress not only led to fine-pitch bonding at sub 100°C with very low external pressure of 0.25 MPa. Retention of stress even in the smaller patterns was clearly observed using conventional non-destructive wafer bow technique and further corroborated using solid mechanic module of COMSOL Multiphysics simulator. The quality of stress engineered fine-pitch bonded sample was examined using the pull test and Idonus Wafer Bonder IR Inspection (WBI) tool. Furthermore, the absence of voids and defect free bonding interface clearly opens up realistic chances for three dimensional (3D) IC integration. Moreover, this novel stress tailoring Cu surface modification prior to bonding is the primary contestant for future heterogeneous integration.
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Direct, CMOS In-Line Process Flow Compatible, Sub 100 °C Cu–Cu Thermocompression Bonding Using Stress Engineering
Electronic Materials Letters, 2018Co-Authors: Asisa Kumar Panigrahi, C. Hemanth Kumar, Shiv Govind Singh, Tamal Ghosh, Siva Rama Krishna VanjariAbstract:Diffusion of atoms across the boundary between two bonding layers is the key for achieving excellent Thermocompression Wafer on Wafer bonding. In this paper, we demonstrate a novel mechanism to increase the diffusion across the bonding interface and also shows the CMOS in-line process flow compatible Sub 100 °C Cu–Cu bonding which is devoid of Cu surface treatment prior to bonding. The stress in sputtered Cu thin films was engineered by adjusting the Argon in-let pressure in such a way that one film had a compressive stress while the other film had tensile stress. Due to this stress gradient, a nominal pressure (2 kN) and temperature (75 °C) was enough to achieve a good quality Thermocompression bonding having a bond strength of 149 MPa and very low specific contact resistance of 1.5 × 10^−8 Ω-cm^2. These excellent mechanical and electrical properties are resultant of a high quality Cu–Cu bonding having grain growth between the Cu films across the boundary and extended throughout the bonded region as revealed by Cross-sectional Transmission Electron Microscopy. In addition, reliability assessment of Cu–Cu bonding with stress engineering was demonstrated using multiple current stressing and temperature cycling test, suggests excellent reliable bonding without electrical performance degradation.
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direct cmos in line process flow compatible sub 100 c cu cu Thermocompression bonding using stress engineering
Electronic Materials Letters, 2018Co-Authors: Asisa Kumar Panigrahi, Shiv Govind Singh, Tamal Ghosh, Hemanth C Kumar, Siva Rama Krishna VanjariAbstract:Diffusion of atoms across the boundary between two bonding layers is the key for achieving excellent Thermocompression Wafer on Wafer bonding. In this paper, we demonstrate a novel mechanism to increase the diffusion across the bonding interface and also shows the CMOS in-line process flow compatible Sub 100 °C Cu–Cu bonding which is devoid of Cu surface treatment prior to bonding. The stress in sputtered Cu thin films was engineered by adjusting the Argon in-let pressure in such a way that one film had a compressive stress while the other film had tensile stress. Due to this stress gradient, a nominal pressure (2 kN) and temperature (75 °C) was enough to achieve a good quality Thermocompression bonding having a bond strength of 149 MPa and very low specific contact resistance of 1.5 × 10−8 Ω-cm2. These excellent mechanical and electrical properties are resultant of a high quality Cu–Cu bonding having grain growth between the Cu films across the boundary and extended throughout the bonded region as revealed by Cross-sectional Transmission Electron Microscopy. In addition, reliability assessment of Cu–Cu bonding with stress engineering was demonstrated using multiple current stressing and temperature cycling test, suggests excellent reliable bonding without electrical performance degradation.
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Low temperature Cu-Cu Thermocompression bonding assisted by electrochemical desorption of a self-assembled monolayer
2014 IEEE 2nd International Conference on Emerging Electronics (ICEE), 2014Co-Authors: Tamal Ghosh, Siva Rama V Krishna, Shiv Govind SinghAbstract:This paper reports low temperature Cu-Cu Thermocompression bonding with the help of self-assembled monolayer (SAM) desorption. SAM layer protects copper from oxidation. It should be desorbed just before bonding. The desorption was carried out using cyclic voltammetry in aqueous potassium hydroxide (KOH) solution. Contact angle measurements carried out before and after desorption indicates successful desorption of SAM. The bonding was carried out at 150 °C and has yielded in excellent bond strength of 520 N.