- Email: [email protected]
Nanoscale hybrid manufacturing process by nano particle deposition system (NPDS) and focused ion beam (FIB)
CIRP Annals - Manufacturing Technology 60 (2011) 583–586
Contents lists available at ScienceDirect
CIRP Annals - Manufacturing Technology jou rnal homep age : ht t p: // ees .e lse vi er. com/ci rp/ def a ult . asp
Nanoscale hybrid manufacturing process by nano particle deposition system (NPDS) and focused ion beam (FIB)§ S.H. Ahn (2)*, D.M. Chun, C.S. Kim School of Mechanical and Aerospace & Institute of Advanced Machinery and Design, Seoul National University, Seoul, Republic of Korea
A R T I C L E I N F O
A B S T R A C T
Keywords: Surface Nano manufacturing Rapid prototyping
A novel nanoscale hybrid manufacturing process was developed by integrating the nano particle deposition system and focused ion beam. Thin films of metals and ceramics were deposited by NPDS which sprays nanosized particles at supersonic speed. FIB was adopted as a nanostructuring, i.e., profile cutting, tool of these thin films. By repeating the deposition and the profile cutting, multi-layered-nanostructures with thickness of 500 nm were made of different materials at room temperature. The room temperature deposition of various materials without using binders and controlled-nanoscale profile cutting provides two unique features of this technology in manufacturing of multi-layer 3D nanostructures. ß 2011 CIRP.
1. Introduction
2. Experimental process
Micro/nanoscale structures, sensors, actuators, and robots have been widely researched for many applications including medical devices, electronics, and military gadgets [1–3]. The conventional lithography process for microelectromechanical systems (MEMS) is one typical process. However, three-dimensional (3D) nanoscale manufacturing faces many challenges, such as limited manufacturing precision, limited product geometry, unintentional chemical reactions, thermal damage, and availability of materials. To improve manufacturing precision, researchers have introduced nanoscale hybrid manufacturing processes that integrate two different processes. For example, electrochemical machining (ECM) has been combined with electrical discharge machining (EDM). Researchers have developed hybrid processes of micro-EDM and laser assembly, laser-ECM, electrolytic in-process dressing (ELID), and other hybrid processes [4,5]. However, these processes still face limitations such as manufacturing precision, product geometry, availability of materials, or processing conditions including high temperatures and wet environments. Other research has focused on rapid manufacturing of nanoscale 3D structures. In this research, a novel nanoscale hybrid manufacturing process was developed by integrating a nano particle deposition system (NPDS) and focused ion beam (FIB) to minimize the limitations of previous processes. NPDS is an additive process for thin film deposition [6], and FIB has various functions such as imaging, etching, implanting, and deposition [7–11], but in this research, FIB was used as a subtractive process for nanoscale etching. As a sample nanoscale 3D structure, Sn (metal) and Al2O3 (ceramic) were deposited as a nanoscale multi-layer structure on silicon wafer using NPDS, and profile cutting was carried out using FIB.
2.1. Nanoscale hybrid manufacturing process
§
Submitted by S.I. Oh (1), Seoul National University, South Korea. * Corresponding author.
0007-8506/$ – see front matter ß 2011 CIRP. doi:10.1016/j.cirp.2011.03.071
NPDS and FIB were integrated in this nanoscale hybrid manufacturing process. NPDS can fabricate metal and ceramic film by spraying nano/microsized particles at room temperature under low vacuum conditions (>25 Torr). NPDS was designed to use metals and ceramics in one process, to scale down particle size, and to increase particle velocity using supersonic nozzles, a vacuum chamber, and other components. NPDS consists of an air compressor, powder feeder, vacuum chamber, and vacuum pump, as shown in Fig. 1. Metal Sn, Ni, ceramic TiO2, and Al2O3 have been deposited [6,12–14]. NPDS provides certain distinctive advantages:
room temperature processing condition, use of various available materials including metals and ceramics, relatively high deposition rate, no post-processing, and dry processing, requiring no binder and no solution.
FIB can be used as a nanoscale etching process. It also provides certain distinctive advantages:
direct writing, ultra-precision processing, room temperature processing condition, use of all solid materials, and no post-processing.
By combining these two processes, a novel nanoscale hybrid manufacturing process was developed. This process can fabricate a nanoscale 3D structure with no thermal damage and no unwanted chemical reactions, using various materials and a short processing time. Fig. 2 shows a schematic view of the integrated hybrid
[()TD$FIG]
584
S.H. Ahn et al. / CIRP Annals - Manufacturing Technology 60 (2011) 583–586
be fabricated. Finally, a nanoscale 3D part can be manufactured after removing supporters and final profile cutting.
[()TD$FIG]
2.2. Deposition
Fig. 1. Schematic image of a nanoparticle deposition system.
Fig. 2. Schematic view of the hybrid manufacturing process integrating NPDS and FIB: the standard referencing device is for the high degree of overlay accuracy and the in situ device is for the measurement of material properties.
[()TD$FIG]
[()TD$FIG]
manufacturing process. Thin films of metals and ceramics can be deposited using NPDS, and FIB was used as a nanostructuring (i.e., profile cutting) tool of these thin films. Through repeated deposition and profile cutting, multi-layered nanostructures with a thickness of 500 nm were formed of various materials at room temperature. Fig. 3 is a process flow chart of the hybrid manufacturing process for nanoscale 3D part. Based on the 3D design, the process planner will slice the part, and create layers. Each layer has different profile and materials including real part and supporter part. Based on this information, material for deposition will be selected and layer deposition will be carried out by NPDS. And the profile cutting will be performed by FIB. By repeating layer deposition and profile cutting, the 3D structure can
Sn (metal) and Al2O3 (ceramic) were deposited as a nanoscale multi-layer structure on Si wafer using NPDS. The order of deposition was Sn, Al2O3, and Sn. The sandwich structure can be used as a nanoscale conductor; Fig. 4 shows a schematic image of the deposited multi-layer. Fig. 5 shows a field emission scanning electron microscopy (FESEM) image of the raw materials. Sn powder with a diameter of less than 10 mm (Sigma–Aldrich) was used for deposition, and Al2O3 powder was submicron or nano-sized and manufactured by Cotronics Corp. (New York, NY, USA). Table 1 lists the process parameters used to deposit both powders. A converging–diverging nozzle with throat dimensions of 1 mm 1 mm and exit dimensions of 1 mm 3 mm was utilized. Both powders were successfully deposited using the same process parameters. The dense film was deposited as shown in Fig. 6. Fig. 6 shows a cross-section image of the Sn/Al2O3/Sn/Si wafer structure. The multi-layer had a thickness of about 2.2 mm. The top layer of the multi-layer structure can be distinguished by cracking due to specimen fracture, but the rest of the border between the Al2O3 and Sn layers is indistinguishable. To confirm the components of each layer, energy dispersive X-ray spectroscopy (EDXs) was used along a line, as shown in Fig. 7. In the substrate, measurements revealed that the intensity of Si was dominant, with large amounts of Sn in the first layer, Al in the middle layer, and Sn and Pt in the top layer. Pt was used as a conductive coating for FE-SEM. When a high energy of electron (15 keV) was scanned across the cross section of Sn/Al2O3, the contrasts of each layer became different, and the layers could be distinguished in the SEM image. 2.3. Profile cutting Profile cutting involved using a commercially available FIB with a maximum resolution of 4 nm, the SMI3050 manufactured by SII Nanotechnology. For this experiment, ion beams were irradiated under conditions of 30 kV of gallium ion energy, 270 pA of ion current, and 5 ms of dwell time. FIB can etch a profile based on an image. Line and rectangular shapes were used for profile cutting, as shown in Fig. 8. The processing time was less than 10 min for complete profile cutting.
Fig. 3. Process flow chart of the hybrid manufacturing process for nanoscale 3D part.
Fig. 4. Schematic image of the deposited multi-layer.
[()TD$FIG]
S.H. Ahn et al. / CIRP Annals - Manufacturing Technology 60 (2011) 583–586
585
Fig. 5. FE-SEM images of raw powders: (a) Sn and (b) Al2O3.
Line and rectangular extrusions were fabricated as shown in Figs. 9 and 10. Both results revealed a clear borderline of Si wafer, and three layers could be distinguished. Some small flaws were observed on the top layer of the line shape. For the rectangular shape, carbon deposition in FIB was carried out to protect the top layer from the ion beam. The repeatability of deposition and profile cutting was confirmed through experiments. First, an Sn layer was deposited on Si wafer using NPDS, and then a simple pocket was etched using FIB. The first Sn layer was separated by the pocket. Second, an Al2O3 layer was deposited, and the pocket was filled with Al2O3. This ceramic-filled pocket can act as an insulator. Finally, a Sn layer was formed. The result was evaluated using a cross-section fabricated by FIB; Fig. 11 shows a cross-section image. The different conductivity of each layer clearly revealed the layers using FIB scanning. The etched pocket was filled with an Al2O3 layer, and the step coverage of NPDS was confirmed.
3. Results and discussion Nanoscale three-layer structures were formed from different materials using a novel nanoscale hybrid manufacturing process under room-temperature processing conditions, using no binder and no additional post-processing. Each layer was clearly recognizable. Depositions of metal and ceramic layers were successful, as was profile cutting. The step coverage was confirmed through the repeated deposition processes in etched profile. The conductive Sn layer could be observed, but the non-conductive Al2O3 layer was hardly observed by a second-electron detector. The grain size of the Sn layer varied because the size of the raw powder varied widely. The raw powder directly influenced deposition results; the thickness of each layer differed from other layers, even if the process parameters were identical. The powder and the surface status affected the deposition results. Finally, the surface was not flat; this is a disadvantage of the spray-deposition process. NPDS processing
[()TD$FIG]
Table 1 Process parameters of NPDS. Parameters
Values
Distance between the substrate and nozzle (mm) Compressor pressure (MPa) Chamber pressure (MPa) Feed rate (mm/s) Flow rate (L/min) Carrier gas Powder material Substrate material
5.0 0.4 0.002–0.005 0.05 15–20 Air Sn, Al2O3 Si wafer
[()TD$FIG]
Fig. 7. FE-SEM image of a cross-section of multi-layer deposition and the line EDS result.
[()TD$FIG]
Fig. 6. FE-SEM image of a cross-section of Sn/Al2O3/Sn deposition on a Si wafer (2 keV electron voltage).
Fig. 8. Images used for FIB profile cutting: (a) line shape and (b) rectangular shape.
[()TD$FIG]
586
S.H. Ahn et al. / CIRP Annals - Manufacturing Technology 60 (2011) 583–586
parameters should be controlled to maximize uniform thickness and minimize surface roughness. Figs. 8 and 9 reveal an inclined wall; vertical wall fabrication is a key issue in Gaussian beam shape based energy beam manufacturing processes such as laser and FIB. 4. Conclusions
Fig. 9. Fabricated line extrusions of the Sn/Al2O3/Sn/Si wafer structure observed at a 30-deg tilt angle.
[()TD$FIG]
This paper described a novel nanoscale hybrid manufacturing process developed by integrating NPDS and FIB. NPDS is an additive process for thin film deposition, and can fabricate metal and ceramic film by spraying nano/microsized particles at room temperature. FIB is a subtractive process used for nanoscale etching; it is ultra-precise, yielding less than 500 nm resolution under room-temperature processing conditions. Neither process requires any binder, solution, or post-processing. The experimental results revealed multi-layer deposition, profile cutting, and repeatability of additive and subtractive processes. This hybrid manufacturing process can fabricate multi-layer nanoscale 3D structures with no thermal damage and no unwanted chemical reactions, using metal and ceramic materials, with a short processing time. Multi-layers were successfully fabricated using metal and ceramic. The thickness of each layer ranged from 0.5 mm to 1 mm. Three-dimensional structures were also fabricated by profile cutting with 500 nm resolution. Finally, experimental results confirmed the repeatability of NPDS and FIB. The pocket fabricated by FIB on the deposited layer was filled by NPDS. Step coverage characteristics were also verified. However, the deposition surface exhibited surface roughness and the thicknesses of each layer differed. Therefore, the deposition process should be controlled and planarization should be considered if necessary. For FIB, it is important to prevent small flaws in the top layer from the ion beam. In addition, it was difficult to fabricate vertical walls. Future research will need to focus on beam control. Acknowledgements This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea Government (MEST) (No. 2010-0029227, No. 2010-0000520 and No. 2010-0028174). References
Fig. 10. Fabricated rectangular extrusion of the Sn/Al2O3/Sn/Si wafer structure observed at a 45-deg tilt angle.
[()TD$FIG]
Fig. 11. Fabricated Sn/Al2O3/Sn/Si wafer structure with an Al2O3 pocket.
[1] Patil M, Mehta DS, Guvva S (2008) Future impact of nanotechnology on medicine and dentistry. Journal of Indian Society of Periodontlogy 12(2):34–40. [2] Altmann J (2004) Military uses of nanotechnology: perspectives and concerns. Security Dialogue 35(1):61–79. [3] Hierold C (2004) From micro- to nanosystems: mechanical sensors go nano. Journal of Micromechanics and Microengineering 14:1–11. [4] Qin Y, Brockett A, Ma Y, Razali A, Zhao J, Harrison C, Pan W, Dai X, Loziak D (2010) Micro-manufacturing: research, technology outcomes and development issues. International Journal of Advanced Manufacturing Technology 47(9–12):821–837. [5] Kuo CL, Huang JD, Liang HY (2003) Fabrication of 3D metal microstructures using a hybrid process of micro-EDM and laser assembly. International Journal of Advanced Manufacturing Technology 21(10–11):796–800. [6] Chun DM, Kim MH, Lee JC, Ahn SH (2008) A nano-particle deposition system for ceramic and metal coating at room temperature and low vacuum conditions. International Journal of Precision Engineering and Manufacturing 9(1): 51–53. [7] Reyntjens S, Puers R (2010) A review of focused ion beam applications in microsystem technology. Journal of Micromechanics and Microengineering 11:287–300. [8] Fang FZ, Xua ZW, Hua XT, Wangc CT, Luoc XG, Fud YQ (2010) Nano-photomask fabrication using focused ion beam direct writing. CIRP Annals – Manufacturing Technology 59(1):543–546. [9] Kim CS, Ahn SH, Jang DY (2010) Nanoscale effects in carbon structures fabricated using focused ion beam-chemical vapour deposition. Thin Solid Films 518(18):5177–5182. [10] Kim CS, Kim HJ, Ahn SH, Jang DY (2010) Morphological influence of the beam overlap in focused ion beam induced deposition using raster scan. Microelectronic Engineering 87(5–8):972–976. [11] Ali MY, Hung W, Yongqi F (2010) A review of focused ion beam sputtering. International Journal of Precision Engineering and Manufacturing 11(1):157–170. [12] Chun DM, Kim MH, Lee JC, Ahn SH (2008) TiO2 coating on metal and polymer substrates by nano particle deposition system (NPDS). CIRP Annals – Manufacturing Technology 57(1):551–554. [13] Chun DM, Kim MS, Yeo JC, Kim MH, Ahn SH, Lee CS (2010) Nano/micro particle beam for ceramic deposition and mechanical etching. Physica Scripta 139T:014047. [14] Jung K, Song W, Chun DM, Kim YH, Yeo JC, Kim MS, Ahn S-H, Lee CS (2010) Nickel line patterning using silicon supersonic micronozzle integrated with a nanoparticle deposition system. Japanese Journal of Applied Physics 49:05EC09.
Contents lists available at ScienceDirect
CIRP Annals - Manufacturing Technology jou rnal homep age : ht t p: // ees .e lse vi er. com/ci rp/ def a ult . asp
Nanoscale hybrid manufacturing process by nano particle deposition system (NPDS) and focused ion beam (FIB)§ S.H. Ahn (2)*, D.M. Chun, C.S. Kim School of Mechanical and Aerospace & Institute of Advanced Machinery and Design, Seoul National University, Seoul, Republic of Korea
A R T I C L E I N F O
A B S T R A C T
Keywords: Surface Nano manufacturing Rapid prototyping
A novel nanoscale hybrid manufacturing process was developed by integrating the nano particle deposition system and focused ion beam. Thin films of metals and ceramics were deposited by NPDS which sprays nanosized particles at supersonic speed. FIB was adopted as a nanostructuring, i.e., profile cutting, tool of these thin films. By repeating the deposition and the profile cutting, multi-layered-nanostructures with thickness of 500 nm were made of different materials at room temperature. The room temperature deposition of various materials without using binders and controlled-nanoscale profile cutting provides two unique features of this technology in manufacturing of multi-layer 3D nanostructures. ß 2011 CIRP.
1. Introduction
2. Experimental process
Micro/nanoscale structures, sensors, actuators, and robots have been widely researched for many applications including medical devices, electronics, and military gadgets [1–3]. The conventional lithography process for microelectromechanical systems (MEMS) is one typical process. However, three-dimensional (3D) nanoscale manufacturing faces many challenges, such as limited manufacturing precision, limited product geometry, unintentional chemical reactions, thermal damage, and availability of materials. To improve manufacturing precision, researchers have introduced nanoscale hybrid manufacturing processes that integrate two different processes. For example, electrochemical machining (ECM) has been combined with electrical discharge machining (EDM). Researchers have developed hybrid processes of micro-EDM and laser assembly, laser-ECM, electrolytic in-process dressing (ELID), and other hybrid processes [4,5]. However, these processes still face limitations such as manufacturing precision, product geometry, availability of materials, or processing conditions including high temperatures and wet environments. Other research has focused on rapid manufacturing of nanoscale 3D structures. In this research, a novel nanoscale hybrid manufacturing process was developed by integrating a nano particle deposition system (NPDS) and focused ion beam (FIB) to minimize the limitations of previous processes. NPDS is an additive process for thin film deposition [6], and FIB has various functions such as imaging, etching, implanting, and deposition [7–11], but in this research, FIB was used as a subtractive process for nanoscale etching. As a sample nanoscale 3D structure, Sn (metal) and Al2O3 (ceramic) were deposited as a nanoscale multi-layer structure on silicon wafer using NPDS, and profile cutting was carried out using FIB.
2.1. Nanoscale hybrid manufacturing process
§
Submitted by S.I. Oh (1), Seoul National University, South Korea. * Corresponding author.
0007-8506/$ – see front matter ß 2011 CIRP. doi:10.1016/j.cirp.2011.03.071
NPDS and FIB were integrated in this nanoscale hybrid manufacturing process. NPDS can fabricate metal and ceramic film by spraying nano/microsized particles at room temperature under low vacuum conditions (>25 Torr). NPDS was designed to use metals and ceramics in one process, to scale down particle size, and to increase particle velocity using supersonic nozzles, a vacuum chamber, and other components. NPDS consists of an air compressor, powder feeder, vacuum chamber, and vacuum pump, as shown in Fig. 1. Metal Sn, Ni, ceramic TiO2, and Al2O3 have been deposited [6,12–14]. NPDS provides certain distinctive advantages:
room temperature processing condition, use of various available materials including metals and ceramics, relatively high deposition rate, no post-processing, and dry processing, requiring no binder and no solution.
FIB can be used as a nanoscale etching process. It also provides certain distinctive advantages:
direct writing, ultra-precision processing, room temperature processing condition, use of all solid materials, and no post-processing.
By combining these two processes, a novel nanoscale hybrid manufacturing process was developed. This process can fabricate a nanoscale 3D structure with no thermal damage and no unwanted chemical reactions, using various materials and a short processing time. Fig. 2 shows a schematic view of the integrated hybrid
[()TD$FIG]
584
S.H. Ahn et al. / CIRP Annals - Manufacturing Technology 60 (2011) 583–586
be fabricated. Finally, a nanoscale 3D part can be manufactured after removing supporters and final profile cutting.
[()TD$FIG]
2.2. Deposition
Fig. 1. Schematic image of a nanoparticle deposition system.
Fig. 2. Schematic view of the hybrid manufacturing process integrating NPDS and FIB: the standard referencing device is for the high degree of overlay accuracy and the in situ device is for the measurement of material properties.
[()TD$FIG]
[()TD$FIG]
manufacturing process. Thin films of metals and ceramics can be deposited using NPDS, and FIB was used as a nanostructuring (i.e., profile cutting) tool of these thin films. Through repeated deposition and profile cutting, multi-layered nanostructures with a thickness of 500 nm were formed of various materials at room temperature. Fig. 3 is a process flow chart of the hybrid manufacturing process for nanoscale 3D part. Based on the 3D design, the process planner will slice the part, and create layers. Each layer has different profile and materials including real part and supporter part. Based on this information, material for deposition will be selected and layer deposition will be carried out by NPDS. And the profile cutting will be performed by FIB. By repeating layer deposition and profile cutting, the 3D structure can
Sn (metal) and Al2O3 (ceramic) were deposited as a nanoscale multi-layer structure on Si wafer using NPDS. The order of deposition was Sn, Al2O3, and Sn. The sandwich structure can be used as a nanoscale conductor; Fig. 4 shows a schematic image of the deposited multi-layer. Fig. 5 shows a field emission scanning electron microscopy (FESEM) image of the raw materials. Sn powder with a diameter of less than 10 mm (Sigma–Aldrich) was used for deposition, and Al2O3 powder was submicron or nano-sized and manufactured by Cotronics Corp. (New York, NY, USA). Table 1 lists the process parameters used to deposit both powders. A converging–diverging nozzle with throat dimensions of 1 mm 1 mm and exit dimensions of 1 mm 3 mm was utilized. Both powders were successfully deposited using the same process parameters. The dense film was deposited as shown in Fig. 6. Fig. 6 shows a cross-section image of the Sn/Al2O3/Sn/Si wafer structure. The multi-layer had a thickness of about 2.2 mm. The top layer of the multi-layer structure can be distinguished by cracking due to specimen fracture, but the rest of the border between the Al2O3 and Sn layers is indistinguishable. To confirm the components of each layer, energy dispersive X-ray spectroscopy (EDXs) was used along a line, as shown in Fig. 7. In the substrate, measurements revealed that the intensity of Si was dominant, with large amounts of Sn in the first layer, Al in the middle layer, and Sn and Pt in the top layer. Pt was used as a conductive coating for FE-SEM. When a high energy of electron (15 keV) was scanned across the cross section of Sn/Al2O3, the contrasts of each layer became different, and the layers could be distinguished in the SEM image. 2.3. Profile cutting Profile cutting involved using a commercially available FIB with a maximum resolution of 4 nm, the SMI3050 manufactured by SII Nanotechnology. For this experiment, ion beams were irradiated under conditions of 30 kV of gallium ion energy, 270 pA of ion current, and 5 ms of dwell time. FIB can etch a profile based on an image. Line and rectangular shapes were used for profile cutting, as shown in Fig. 8. The processing time was less than 10 min for complete profile cutting.
Fig. 3. Process flow chart of the hybrid manufacturing process for nanoscale 3D part.
Fig. 4. Schematic image of the deposited multi-layer.
[()TD$FIG]
S.H. Ahn et al. / CIRP Annals - Manufacturing Technology 60 (2011) 583–586
585
Fig. 5. FE-SEM images of raw powders: (a) Sn and (b) Al2O3.
Line and rectangular extrusions were fabricated as shown in Figs. 9 and 10. Both results revealed a clear borderline of Si wafer, and three layers could be distinguished. Some small flaws were observed on the top layer of the line shape. For the rectangular shape, carbon deposition in FIB was carried out to protect the top layer from the ion beam. The repeatability of deposition and profile cutting was confirmed through experiments. First, an Sn layer was deposited on Si wafer using NPDS, and then a simple pocket was etched using FIB. The first Sn layer was separated by the pocket. Second, an Al2O3 layer was deposited, and the pocket was filled with Al2O3. This ceramic-filled pocket can act as an insulator. Finally, a Sn layer was formed. The result was evaluated using a cross-section fabricated by FIB; Fig. 11 shows a cross-section image. The different conductivity of each layer clearly revealed the layers using FIB scanning. The etched pocket was filled with an Al2O3 layer, and the step coverage of NPDS was confirmed.
3. Results and discussion Nanoscale three-layer structures were formed from different materials using a novel nanoscale hybrid manufacturing process under room-temperature processing conditions, using no binder and no additional post-processing. Each layer was clearly recognizable. Depositions of metal and ceramic layers were successful, as was profile cutting. The step coverage was confirmed through the repeated deposition processes in etched profile. The conductive Sn layer could be observed, but the non-conductive Al2O3 layer was hardly observed by a second-electron detector. The grain size of the Sn layer varied because the size of the raw powder varied widely. The raw powder directly influenced deposition results; the thickness of each layer differed from other layers, even if the process parameters were identical. The powder and the surface status affected the deposition results. Finally, the surface was not flat; this is a disadvantage of the spray-deposition process. NPDS processing
[()TD$FIG]
Table 1 Process parameters of NPDS. Parameters
Values
Distance between the substrate and nozzle (mm) Compressor pressure (MPa) Chamber pressure (MPa) Feed rate (mm/s) Flow rate (L/min) Carrier gas Powder material Substrate material
5.0 0.4 0.002–0.005 0.05 15–20 Air Sn, Al2O3 Si wafer
[()TD$FIG]
Fig. 7. FE-SEM image of a cross-section of multi-layer deposition and the line EDS result.
[()TD$FIG]
Fig. 6. FE-SEM image of a cross-section of Sn/Al2O3/Sn deposition on a Si wafer (2 keV electron voltage).
Fig. 8. Images used for FIB profile cutting: (a) line shape and (b) rectangular shape.
[()TD$FIG]
586
S.H. Ahn et al. / CIRP Annals - Manufacturing Technology 60 (2011) 583–586
parameters should be controlled to maximize uniform thickness and minimize surface roughness. Figs. 8 and 9 reveal an inclined wall; vertical wall fabrication is a key issue in Gaussian beam shape based energy beam manufacturing processes such as laser and FIB. 4. Conclusions
Fig. 9. Fabricated line extrusions of the Sn/Al2O3/Sn/Si wafer structure observed at a 30-deg tilt angle.
[()TD$FIG]
This paper described a novel nanoscale hybrid manufacturing process developed by integrating NPDS and FIB. NPDS is an additive process for thin film deposition, and can fabricate metal and ceramic film by spraying nano/microsized particles at room temperature. FIB is a subtractive process used for nanoscale etching; it is ultra-precise, yielding less than 500 nm resolution under room-temperature processing conditions. Neither process requires any binder, solution, or post-processing. The experimental results revealed multi-layer deposition, profile cutting, and repeatability of additive and subtractive processes. This hybrid manufacturing process can fabricate multi-layer nanoscale 3D structures with no thermal damage and no unwanted chemical reactions, using metal and ceramic materials, with a short processing time. Multi-layers were successfully fabricated using metal and ceramic. The thickness of each layer ranged from 0.5 mm to 1 mm. Three-dimensional structures were also fabricated by profile cutting with 500 nm resolution. Finally, experimental results confirmed the repeatability of NPDS and FIB. The pocket fabricated by FIB on the deposited layer was filled by NPDS. Step coverage characteristics were also verified. However, the deposition surface exhibited surface roughness and the thicknesses of each layer differed. Therefore, the deposition process should be controlled and planarization should be considered if necessary. For FIB, it is important to prevent small flaws in the top layer from the ion beam. In addition, it was difficult to fabricate vertical walls. Future research will need to focus on beam control. Acknowledgements This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea Government (MEST) (No. 2010-0029227, No. 2010-0000520 and No. 2010-0028174). References
Fig. 10. Fabricated rectangular extrusion of the Sn/Al2O3/Sn/Si wafer structure observed at a 45-deg tilt angle.
[()TD$FIG]
Fig. 11. Fabricated Sn/Al2O3/Sn/Si wafer structure with an Al2O3 pocket.
[1] Patil M, Mehta DS, Guvva S (2008) Future impact of nanotechnology on medicine and dentistry. Journal of Indian Society of Periodontlogy 12(2):34–40. [2] Altmann J (2004) Military uses of nanotechnology: perspectives and concerns. Security Dialogue 35(1):61–79. [3] Hierold C (2004) From micro- to nanosystems: mechanical sensors go nano. Journal of Micromechanics and Microengineering 14:1–11. [4] Qin Y, Brockett A, Ma Y, Razali A, Zhao J, Harrison C, Pan W, Dai X, Loziak D (2010) Micro-manufacturing: research, technology outcomes and development issues. International Journal of Advanced Manufacturing Technology 47(9–12):821–837. [5] Kuo CL, Huang JD, Liang HY (2003) Fabrication of 3D metal microstructures using a hybrid process of micro-EDM and laser assembly. International Journal of Advanced Manufacturing Technology 21(10–11):796–800. [6] Chun DM, Kim MH, Lee JC, Ahn SH (2008) A nano-particle deposition system for ceramic and metal coating at room temperature and low vacuum conditions. International Journal of Precision Engineering and Manufacturing 9(1): 51–53. [7] Reyntjens S, Puers R (2010) A review of focused ion beam applications in microsystem technology. Journal of Micromechanics and Microengineering 11:287–300. [8] Fang FZ, Xua ZW, Hua XT, Wangc CT, Luoc XG, Fud YQ (2010) Nano-photomask fabrication using focused ion beam direct writing. CIRP Annals – Manufacturing Technology 59(1):543–546. [9] Kim CS, Ahn SH, Jang DY (2010) Nanoscale effects in carbon structures fabricated using focused ion beam-chemical vapour deposition. Thin Solid Films 518(18):5177–5182. [10] Kim CS, Kim HJ, Ahn SH, Jang DY (2010) Morphological influence of the beam overlap in focused ion beam induced deposition using raster scan. Microelectronic Engineering 87(5–8):972–976. [11] Ali MY, Hung W, Yongqi F (2010) A review of focused ion beam sputtering. International Journal of Precision Engineering and Manufacturing 11(1):157–170. [12] Chun DM, Kim MH, Lee JC, Ahn SH (2008) TiO2 coating on metal and polymer substrates by nano particle deposition system (NPDS). CIRP Annals – Manufacturing Technology 57(1):551–554. [13] Chun DM, Kim MS, Yeo JC, Kim MH, Ahn SH, Lee CS (2010) Nano/micro particle beam for ceramic deposition and mechanical etching. Physica Scripta 139T:014047. [14] Jung K, Song W, Chun DM, Kim YH, Yeo JC, Kim MS, Ahn S-H, Lee CS (2010) Nickel line patterning using silicon supersonic micronozzle integrated with a nanoparticle deposition system. Japanese Journal of Applied Physics 49:05EC09.