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A versatile solvent-free method for surface modification of various materials including both metals and polymers is described. Strong irreversible bonds were formed when substrates modified by initiated chemical vapor deposition (iCVD) of poly(1,3,5-trivinyltrimethylcyclotrisiloxane) or poly(V3D3) and exposed to an oxygen plasma were brought into contact with plasma-treated poly(dimethylsiloxane) (PDMS). The strength of these bonds was quantified by burst pressure testing microfluidic channels in the PDMS. The burst pressures of PDMS bonded to various coated substrates were in some cases comparable to that of PDMS bonded directly to PDMS. In addition, porous PTFE membrane coated with poly(V3D3) was successfully bonded to a PDMS microfluidic device and withstood pressures of over 300 mmHg. Bond strength was shown to correlate with surface roughness and quality of the bond between the coating and substrate. This work paves a methodology to fabricate microfluidic devices that include a specifically tailored membrane. Furthermore, the bonded devices exhibited hydrolytic stability; no dramatic change was observed even after immersion in water at room temperature over a period of 10 days.

Membranes for a lung assist device must permit the exchange of gaseous O₂ and CO₂ while simultaneously acting as a liquid barrier, so as to prevent leakage of blood and its components from passing from one side to the other. Additionally, these membranes must be capable of being integrated into microfluidic devices possessing a vascular network. In this work, uniform, large-area, ultra-thin, polymeric free-standing membranes (FSMs) and composite membranes (CMs) are reproducibly fabricated by initiated Chemical Vapor Deposition (iCVD). The 5 μm thick FSMs remained intact during handling and exhibited a CO₂ permeance that was 1.3 times that of the control membrane (8 μm thick spun-cast membrane of silicone). The CMs consisted of a dense iCVD skin layer (0.5-3 μm thick) deposited on top of a polytetrafluoroethylene (PTFE) support membrane (20 μm thick, 100 nm pores). The CMs exhibited CO₂ and O₂ permeance values 50-300 times that of the control membrane. The FSMs were subjected to mechanical testing to assess the impact of the absence of an underlying support structure. The CMs were subjected to liquid barrier tests to ensure that while they were permeable to gases, they acted as barriers to liquids. Both FSMs and CMs were integrated into silicone microfluidic devices and tested for bond integrity.

Chemical vapor deposition (CVD) polymerization utilizes the delivery of vapor-phase monomers to form chemically well-defined polymeric films directly on the surface of a substrate. CVD polymers are desirable as conformal surface modification layers exhibiting strong retention of organic functional groups, and, in some cases, are responsive to external stimuli. Traditional wet-chemical chain- and step-growth mechanisms guide the development of new heterogeneous CVD polymerization techniques. Commonality with inorganic CVD methods facilitates the fabrication of hybrid devices. CVD polymers bridge microfabrication technology with chemical, biological, and nanoparticle systems and assembly. Robust interfaces can be achieved through covalent grafting enabling high-resolution (60 nm) patterning, even on flexible substrates. Utilizing only low-energy input to drive selective chemistry, modest vacuum, and room-temperature substrates, CVD polymerization is compatible with thermally sensitive substrates, such as paper, textiles, and plastics. CVD methods are particularly valuable for insoluble and infusible films, including fluoropolymers, electrically conductive polymers, and controllably crosslinked networks and for the potential to reduce environmental, health, and safety impacts associated with solvents. Quantitative models aid the development of large-area and roll-to-roll CVD polymer reactors. Relevant background, fundamental principles, and selected applications are reviewed.

Vapor based polymer deposition methods have evolved to address the limitations of solution polymerization. However this field of vapor based polymerization suffers from varied nomenclature and would benefit from a review article that brought together the different approaches to vapor based polymerization with an effort to present existing nomenclature, clearly identify the various approaches within this field and summarize recent results. This review article is written with the purpose of compiling recent advances in vapor based deposition methods of polymers with a focus on applications that will continue to drive research in this field. We hope that this article encourages researchers engineering novel polymer applications to give vapor based polymerization a serious consideration apart from solution polymerization methods.

Segmented CVD reactor designs enabling spatial control of across-wafer gas phase composition were evaluated for depositing graded films suitable for combinatorial studies. Specifically, two reactor designs were constructed and evaluated with experiments and response surface model (RSM) based analysis to quantify the reactor performance in terms of film thickness uniformity, sensitivity to adjustable reactor operating conditions, range of thickness over which uniformity could be achieved and each reactor's ability to control the thickness gradient across the wafer surface. Design features distinguishing the two reactor systems and their influence on gradient control vs. deposition rate performance are summarized. RSMs relating wafer state properties to process recipes are shown to be effective tools to quantify, qualify and compare different reactor designs.

A 300 amu closed-ion-source RGA (Leybold-Inficon Transpector 2) sampling gases directly from the reactor of an ULVAC ERA-1000 cluster tool has been used for real time process monitoring of a W CVD process. The process involves H2 reduction of WF6 at a total pressure of 67 Pa (0.5 torr) to produce W films on Si wafers heated at temperatures around 350 °C. The normalized RGA signals for the H2 reagent depletion and the HF product generation were correlated with the W film weight as measured post-process with an electronic microbalance for the establishment of thin-film weight (thickness) metrology. The metrology uncertainty (about 7% for the HF product) was limited primarily by the very low conversion efficiency of the W CVD process (around 2-3%). The HF metrology was then used to drive a robust run-to-run control algorithm, with the deposition time selected as the manipulated (or controlled) variable. For that purpose, during a 10 wafer run, a systematic process drift was introduced as a −5 °C processing t...

We have developed a series of interactive control education modules. They are intended to be useful to a broad audience of students as well as practitioners. Their main objective is to provide insight and intuition rather than precise mathematics.

We are developing six control engineering design modules for use by graduate students, advanced undergraduates, and practicing engineers in learning about process control. This is part of a larger project investigating the use of dynamic simulation and visualization to enhance the education of manufacturing engineers, technicians and operators. The crucial motivating ideas are that active learning can substantially enhance education-a widely accepted idea-and that computer-based dynamic simulation and visualization can induce active learning. The modules cover the fundamentals of control engineering as well as an introduction to run-to-run control. Each module requires the student to interact, in real time, with an animated illustration of the process to be controlled or the control concept being discussed. The next step is the evaluation of the effectiveness of this teaching tool.

Mass spectrometry has proven valuable in understanding and controlling chemical processes used in semiconductor fabrication. Given the complexity of spatial distributions of fluid flow, thermal, and chemical parameters in such processes, multipoint chemical sampling would be beneficial. The authors have designed and implemented a multiplexed mass spectrometric gas sampling system for real-time, in situ measurement of gas species concentrations at multiple locations in a spatially programmable chemical vapor deposition (SP-CVD) reactor prototype, where such chemical sensing is essential to achieve the benefits of a new paradigm for reactor design. The spatially programmable reactor, in which across-wafer distributions of reactant are programmable, enables (1) uniformity at any desired process design point, or (2) intentional nonuniformity to accelerate process optimization through combinatorial methods. The application of multiplexed mass spectrometric sensing is well suited to our SP-CVD design, which is unique in effectively segmenting the showerhead gas flows by using exhaust gas pumping through the showerhead for each segment. In turn, mass spectrometric sampling signals for each segment are multiplexed to obtain real-time signatures of reactor spatial behavior. Here the authors report results using inert gases to study the spatial distributions of species, validate SP-CVD reactor models, and lead to an understanding of fundamental phenomena associated with the reactor design. This forms the basis for using real-time mass spectrometry to drive process sensing, metrology, and control in such reactor systems.

A new chemical vapor deposition (CVD) reactor design was developed to intentionally induce spatially nonuniform film thickness deposition patterns on a single wafer. A segmented showerhead design allows individual regions of a wafer to be exposed to different precursor concentrations simultaneously during a run resulting in different thickness profiles on the wafer and a thickness gradient at the boundaries between segment regions. Different recipes were cycled through each of the segments in a sequence of deposition experiments to develop a model relating precursor concentration to film thickness in each segment region. As a demonstration of spatial programmability, the system was reprogramed using this model to produce uniform thickness amongst the segments; intersegment uniformity approaching 0.60% (thickness standard deviation) was demonstrated. Potential applications of this reactor design to combinatorial CVD are discussed.

Run to run control with an Internal Model Control (IMC) approach has been used for wafer state (thickness) control in the tungsten chemical vapor deposition (CVD) process. The control implementation was preceded by establishing a stable wafer state thickness metrology using in situ mass spectrometry. Direct reactor sampling was achieved from an Ulvac ERA-1000 cluster tool module during the H2/WF6 W CVD process at 0.5 Torr for temperatures 350–400 °C using a 300 amu closed ion source Inficon Transpector system. Signals from HF product generation were used for in-process thickness metrology and compared to ex situ, postprocess thickness measurements obtained by microbalance mass measurements, providing a metrology accuracy of about 7% (limited primarily by the very low conversion efficiency of the process used, ∼2%–3%). A deliberate systematic process drift was introduced as a −5 °C temperature change for each successive wafer, which would have led to a major (∼50%) thickness decrease over ten wafers in an open loop system. A robust run to run (RtR) control algorithm was used to alter the process time in order to maintain constant HF sensing signal obtained from the mass spectrometer, resulting in thickness control comparable to the metrology accuracy. The efficacy of the control algorithm was also corroborated by additional experiments that utilized direct film weight measurements through the use of the microbalance. A set of simulations in Matlab® preceded the control implementation and helped in tuning the controller parameters. These results suggest that in situ chemical sensing, and particularly mass spectrometry, provide the basis for wafer state metrology as needed to achieve RtR control. Furthermore, since the control was consistent with the metrology accuracy, we anticipate significant improvements for processes used in manufacturing, where conversion rates are much higher (40%–50%) and corresponding signals for metrology will be much larger.Run to run control with an Internal Model Control (IMC) approach has been used for wafer state (thickness) control in the tungsten chemical vapor deposition (CVD) process. The control implementation was preceded by establishing a stable wafer state thickness metrology using in situ mass spectrometry. Direct reactor sampling was achieved from an Ulvac ERA-1000 cluster tool module during the H2/WF6 W CVD process at 0.5 Torr for temperatures 350–400 °C using a 300 amu closed ion source Inficon Transpector system. Signals from HF product generation were used for in-process thickness metrology and compared to ex situ, postprocess thickness measurements obtained by microbalance mass measurements, providing a metrology accuracy of about 7% (limited primarily by the very low conversion efficiency of the process used, ∼2%–3%). A deliberate systematic process drift was introduced as a −5 °C temperature change for each successive wafer, which would have led to a major (∼50%) thickness decrease over ten wafers in an ...