2,190 research outputs found
Auto Defect Classification (ADC) Value for Patterned Wafer Inspection Systems in PLY Within a High Volume Wafer Manufacturing Fabrication Facility
The purpose of this investigation is to demonstrate value for Auto Defect
Classification (ADC) for patterned wafer inspection systems within a high volume
manufacturing fabrication in the Process Limited Yield (PLY) defect area. Process
excursions in all functional Unit Process (UP) areas, examples are of etch, litho,
diffusion, are monitored by PLY.
Troubleshooting of process excursions using added defect density count with a
small percentage (random or largest 50 examples) of and inline Scanning Electron
Microscope (SEM) data classification review does not give a clear indication of the full
wafer data. Statistical Process Control (SPC) trigging on total counts or defect density is
not as powerful as making excursion decisions on classified data from ADC (Fisher,
2002).
The ADC data gives classification of the entire wafer rather than a smaller sample
making signature analysis to be an additional troubleshooting tool. The inline ADC data
does not have near the resolution of the SEM but can be used to help make important
decisions to what is occurring in the manufacturing line. The interest is to gain a full
understanding of the current capabilities and limitation of ADC and to apply the learning
to enable faster reaction and visibility into process and tool excursions within a high
volume manufacturing fabrication.
The Technical Learning Vehicle (TLV), high running product layer at the leading
design rule, there were approximately 10,000 wafers a week with 1000 wafer die (chips)
per wafer. A sustained improvement in yield of 1% across the entire manufacturing line
would equate to almost 1 million dollars a month of saving. With the ability to tightly
control multiple etch process tools, the resulting yield improvement was 3% across 15%
of the line. With the baseline yield improvement along with ability to react quickly to
process excursions, the combined improvement resulted in excessive of 5 million dollar a
year of reoccurring savings
Matching Japan in quality : how the leading U.S. semiconductor firms caught up with the best in Japan
Includes bibliographical references.William F. Finan
Virtual metrology for plasma etch processes.
Plasma processes can present dicult control challenges due to time-varying dynamics
and a lack of relevant and/or regular measurements. Virtual metrology (VM) is the
use of mathematical models with accessible measurements from an operating process to
estimate variables of interest. This thesis addresses the challenge of virtual metrology
for plasma processes, with a particular focus on semiconductor plasma etch.
Introductory material covering the essentials of plasma physics, plasma etching, plasma
measurement techniques, and black-box modelling techniques is rst presented for readers
not familiar with these subjects. A comprehensive literature review is then completed
to detail the state of the art in modelling and VM research for plasma etch processes.
To demonstrate the versatility of VM, a temperature monitoring system utilising a
state-space model and Luenberger observer is designed for the variable specic impulse
magnetoplasma rocket (VASIMR) engine, a plasma-based space propulsion system. The
temperature monitoring system uses optical emission spectroscopy (OES) measurements
from the VASIMR engine plasma to correct temperature estimates in the presence of
modelling error and inaccurate initial conditions. Temperature estimates within 2% of
the real values are achieved using this scheme.
An extensive examination of the implementation of a wafer-to-wafer VM scheme to estimate
plasma etch rate for an industrial plasma etch process is presented. The VM
models estimate etch rate using measurements from the processing tool and a plasma
impedance monitor (PIM). A selection of modelling techniques are considered for VM
modelling, and Gaussian process regression (GPR) is applied for the rst time for VM
of plasma etch rate. Models with global and local scope are compared, and modelling
schemes that attempt to cater for the etch process dynamics are proposed. GPR-based
windowed models produce the most accurate estimates, achieving mean absolute percentage
errors (MAPEs) of approximately 1:15%. The consistency of the results presented
suggests that this level of accuracy represents the best accuracy achievable for
the plasma etch system at the current frequency of metrology.
Finally, a real-time VM and model predictive control (MPC) scheme for control of
plasma electron density in an industrial etch chamber is designed and tested. The VM
scheme uses PIM measurements to estimate electron density in real time. A predictive
functional control (PFC) scheme is implemented to cater for a time delay in the VM
system. The controller achieves time constants of less than one second, no overshoot,
and excellent disturbance rejection properties. The PFC scheme is further expanded by
adapting the internal model in the controller in real time in response to changes in the
process operating point
Free-carrier effects in polycrystalline silicon-on-insulator photonic devices
Photonic systems integrated into microelectronic systems using the well established integrated chips fabrication technologies offer immense opportunity in overcoming the bandwidth and power limitations IC faces. The use of deposited polycrystalline silicon in the fabrication of photonic devices has the potential of offering monolithic integration, promising electrical and optical properties, under optimized micro-fabrication, and lower costs. In this thesis, the design, fabrication and optical testing of waveguide devices on polycrystalline silicon platform is presented. Single mode polysilicon waveguide devices were fabricated at the RIT SMFL. The polysilicon waveguides fabricated successfully coupled and guided light. The transmission was measured over several lengths and the cut back method was used to quantify the free carrier absorption and propagation losses of polysilicon at 1550 nm wavelength. Comparisons were made with data for crystalline silicon. The absorption coefficient for polysilicon was found to be 25.9% higher than that of crystalline silicon
Virtual metrology for plasma etch processes.
Plasma processes can present dicult control challenges due to time-varying dynamics
and a lack of relevant and/or regular measurements. Virtual metrology (VM) is the
use of mathematical models with accessible measurements from an operating process to
estimate variables of interest. This thesis addresses the challenge of virtual metrology
for plasma processes, with a particular focus on semiconductor plasma etch.
Introductory material covering the essentials of plasma physics, plasma etching, plasma
measurement techniques, and black-box modelling techniques is rst presented for readers
not familiar with these subjects. A comprehensive literature review is then completed
to detail the state of the art in modelling and VM research for plasma etch processes.
To demonstrate the versatility of VM, a temperature monitoring system utilising a
state-space model and Luenberger observer is designed for the variable specic impulse
magnetoplasma rocket (VASIMR) engine, a plasma-based space propulsion system. The
temperature monitoring system uses optical emission spectroscopy (OES) measurements
from the VASIMR engine plasma to correct temperature estimates in the presence of
modelling error and inaccurate initial conditions. Temperature estimates within 2% of
the real values are achieved using this scheme.
An extensive examination of the implementation of a wafer-to-wafer VM scheme to estimate
plasma etch rate for an industrial plasma etch process is presented. The VM
models estimate etch rate using measurements from the processing tool and a plasma
impedance monitor (PIM). A selection of modelling techniques are considered for VM
modelling, and Gaussian process regression (GPR) is applied for the rst time for VM
of plasma etch rate. Models with global and local scope are compared, and modelling
schemes that attempt to cater for the etch process dynamics are proposed. GPR-based
windowed models produce the most accurate estimates, achieving mean absolute percentage
errors (MAPEs) of approximately 1:15%. The consistency of the results presented
suggests that this level of accuracy represents the best accuracy achievable for
the plasma etch system at the current frequency of metrology.
Finally, a real-time VM and model predictive control (MPC) scheme for control of
plasma electron density in an industrial etch chamber is designed and tested. The VM
scheme uses PIM measurements to estimate electron density in real time. A predictive
functional control (PFC) scheme is implemented to cater for a time delay in the VM
system. The controller achieves time constants of less than one second, no overshoot,
and excellent disturbance rejection properties. The PFC scheme is further expanded by
adapting the internal model in the controller in real time in response to changes in the
process operating point
Electric design of the Power Processing Unit for Pulsed Plasma Thrusters for CubeSat applications.
The opening of space to the private and academic sector has cause a rapid increase in the activities on this field during the last two decades. This movement is known as New Space, where by creating collaborations between governments, private industry and universities is defining what could be the new space race. The use of nano-satellites, in special CubeSats, the creation of more specific missions has risen with them the necessity of more complex subsystems. Odysseus Space Inc in collaboration with the National Cheng Kung University (NCKU), decided to create a propulsion system where Pulsed Plasma Thrusters (PPTs) are targeted as an Attitude Control System (ACS) for CubeSats. Pulsed Plasma Thrusters have a great legacy being the first electric propulsion thruster to flight in space. Nevertheless, PPTs faced an apparent abandonment for the use of more efficient technologies, it has been brought to CubeSats due its robustness and scalability. This work presents different approaches to develop a modular power processing unit (PPU) for PPTs for Cubesats applications, resulting in a functional PPU which meets the tight budget of 10X10X10 cm that conforms the CubeSat Unit standard. Each chapter covers a brief review of the concepts, their analysis and the description of their development while facing the challenges that brings to manage voltages in the order of kilo volts in such small spatial budget. Finally, using a combination of high gain Fly-back and Cockcroft-Walton voltage multiplier topologies for the sparkplug circuit, a main discharge and control circuit are prototyped and tested as part of the PPU, making the baseline for further investigations
Solar photocatalysis for water disinfection: Materials and reactor design
As of 2010, access to clean drinking water is a human right according to UN regulations. Nevertheless, the number of people living in areas without safe drinking water is predicted to increase by three billion by the end of this decade. Several recent cases of E. coli and Cryptosporidium contamination in drinking water are also reported in a number of advanced countries. Therefore ensuring the potability of drinking water is urgent, but highly challenging to both the developing and developed world in the future. A combination of solar disinfection and photocatalysis technology offers real possibilities for removing lethal pathogenic microroganisms from drinking water. The time taken for the conventional SODIS process can be greatly reduced by semiconductor (e.g. TiO2, ZnO, nano-heterojunctions) based photocatalysis. This review addresses the fundamental reaction mechanism, advances in materials synthesis and selection and recent developments in the reactor design for solar energy driven photocatalysis using titanium dioxide. The major advantage of using photo-reactors is that they enhance disinfection by increasing photon flux into the photocatalyst. Other major factors affecting such efficiency of solar-based photocatalysis such as the illuminated volume/total volume ratio, catalyst load and flow rate, are discussed in detail. The significance of using immobilised catalysts over the catalyst powder in slurries is also highlighted. It is noted that, despite encouraging early field studies, the commercialisation and mass production of solar photocatalysis systems remains highly challenging. Recommendations for future directions for addressing issues such as mass transfer, requirement of a standard test method, photo-reactors design and visible light absorption by TiO2 coatings are also discussed
Improvement Of Change Glue Schedule Down Time At Lid Attachment Process For Semiconductor Devices
This research report presents the work done on the improvement of change glue schedule down time at lid attachment process for semiconductor devices. Lid attachment is the end of line process for Plastic Dual Small Outline Flat (PDSOF) package which is one of the
semiconductor devices. The process is started with pick and places the lid onto the package, then proceeds to glue dispensing with dosage on four corners of the lids to completely seal the package by using capillary effect. There is a change of glue activity in this process which is counted under schedule down time. Based on the Overall Equipment Effectiveness (OEE), it was found that the change of glue activity give impact on the machine performance. The increasing of change glue time will result in the production did not achieve the target productivity. In this research, the hidden losses were defined on the equipment setup which is changed of glue in the lid attachment process. There is plan to increase the amount of glue lid attach to reduce the schedule down time in order to improve overall equipment effectiveness toward achieving good productivity. The study for glue pot life is required since increasing the amount of glue will extend the glue pot life
and it is suspected will increase the glue viscosity. In general, all the project objective are managed to be achieved using the developed research methodology. For future work, this research should be enhance further to achieve better result and to make use of the increasing glue amount and pot life extended time enhancement in other perspective field and also to carry out further study to improve on the whitish on lid surface
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