El trabajo de investigación que se describe en la presente memoria se plantea como objetivo el desarrollo de un EnFET con aplicación clínica en la medición de la concentración de urea de manera indirecta en líquido dializado para propósito de diagnóstico clínico más rápido, exacto y utilizando pequeñas cantidades de componentes químicos, específicamente en diálisis. El ENFET implementado atiende a la reacción química en donde la urea es catalizada por la enzima ureasa, utilizando una membrana enzimática con la ureasa como la enzima escogida. Para conseguir el objetivo planteado, se ha diseñado y puesto a punto la tecnología de fabricación del ISFET. Sobre la base de los resultados obtenidos por el propio autor en el desarrollo de su tesina, se ha desarrollado el tratamiento previo del transductor ISFET, su acondicionamiento y obtención de la sensibilidad adecuada para la aplicación clínica que se persigue. Se ha puesto también a punto el proceso de formación de la membrana enzimáticaconveniente, así como la técnica de inmovilización de la enzima ureasa y la "fijación" de la enzima ureasa sobre el transductor ISFET. La fijación de la membrana es uno de los puntos críticos del micro-sensor puesto que el período de vida del dispositivo depende totalmente de la "calidad" de la misma. Finalmente se han caracterizado en laboratorio los dispositivos EnFET obtenidos.El trabajo realizado ha generado un ENFET de fácil industrialización, con un tiempo de vida superior a dos meses y medio, eficiente para la medida indirecta de la concentración de urea en sangre a partir de la medida de la concentración de urea en el líquido dializado. El dispositivo se ha verificado en laboratorio realizando medidas de la concentración de urea sobre muestras ideales y comparando las medidas obtenidas con el dispositivo con medidas realizadas según procedimientos analíticos convencionales.Los parámetros del ENFET que reflejan su excelente calidad son Sensibilidad (mV/dec urea): 77.02; Límite inferior de respuesta lineal: 3.10-4 M; Rango lineal de Detección: 3.10-4 M - 2.10-3 M ;Tiempo de respuesta: 90s; Estabilidad del potencial medido: ±0.3mV; Tiempo de vida: 75 días. Los ENFETs desarrollados fueron sometidos a pruebas de reproducibilidad o repetitividad de la respuesta observándose que satisfacen ampliamente los requerimientos consistentes en que se obtienen valores de potencial eléctrico de valores similares en 10 mediciones efectuadas en dos días consecutivos. La desviación de los valores medidos respecto al valor promedio (253.61mV) aparece entre -0.34mV a 0.50mV. Estos valores del potencial eléctrico que aparece en la interfase membrana enzimática-óxido del ISFET, prácticamente constantes, y que esta relacionado en forma indirecta con la concentración de urea en la solución, permiten asegurar el buen desempeño del ENFET en pruebas reales en trabajo continuo. Posteriormente, el dispositivo se ha validado en aplicación realizando medidas de concentración de urea en muestras de liquido dializado de pacientes del Hospital Parc Tauli recogidas en distintas etapas del proceso de diálisis y procediendo a comparar y hacer las correlaciones respectivas con los valores medidos sobre las mismas muestras por un laboratorio comercial mostrándose que la diferencias en las medidas son del orden de 2.5%.

Point-of-care (POC) diagnostics presents a giant market opportunity with profound societal impact. In particular, specific detection of DNA and protein markers can be essential for early diagnosis of e.g. cancer, cardiovascular disease, infections or allergies. Today, identification of these markers often requires extensive laboratory work and hence is expensive and time consuming. Current methods for recognition and detection of specific biomolecules are mostly optics based and thus impose severe limitations as to convenience, specificity, sensitivity, parallel processing and cost reduction. Electronic sensors based on silicon nanowire field-effect transistors have been reported to be able to detect biomolecules with concentrations down to femtomolar (fM) level with high specificity. Although the reported capability needs further confirmation, the CMOS-compatible fabrication process of such sensors allows for low cost production and high density integration, which are favorable for POC applications. This thesis mainly focuses on the development of a multiplex detection platform based on silicon nanowire field-effect sensors integrated with a microfluidic system for liquid sample delivery. Extensive work was dedicated to developing a top-down fabrication process of the sensors as well as an effective passivation scheme. The operation mechanism and coupling efficiencies of different gate configurations were studied experimentally with the assistance of numerical simulation and equivalent circuits. Using pH sensing as a model system, large effort was devoted to identifying sources for false responses resulting from the instability of the inert-metal gate electrode. In addition, the drift mechanism of the sensor operating in electrolyte was addressed and a calibration model was proposed. Furthermore, protein detection experiments were performed using small-sized Affibody molecules as receptors on the gate insulator to tackle the Debye screening issue. Preliminary results showed that the directionality of the current changes in the sensors was in good agreement with the charge polarities of the proteins. Finally, a graphene-based capacitor was examined as an alternative to the nanowire device for field-effect ion sensing. Our initial attempts showed some attractive features of the capacitor sensor.

El trabajo realizado para la tesis se ha centrado en el desarrollo y el estudio de multi-sensores químicos basados en silicio para aplicaciones biomédicas. Dicho trabajo se divide en tres partes:En la primera parte se han fabricado sensores de silicio basados en transistores de efecto de campo sensibles a iones (ISFET). El dispositivo tiene forma de aguja e incluye dos sensores ISFETs, un pseudo-electrodo de referencia de platino y un sensor de temperatura basado en una resistencia de platino. Los ISFETs se han caracterizado eléctricamente como transistores MOSFET y químicamente como sensores de pH, con resultados satisfactorios, lo que ha demostrado la viabilidad de las tecnologías de fabricación.Se han desarrollado MEMFETs selectivos al ión potasio depositando sobre el ISFET una membrana polimérica de PVC que contiene la valinomicina como ionóforo. Los sensores mostraron una respuesta de 50 mV/década aproximadamente, en un rango de actividad del ión K+ que va desde 10-4 M hasta 10-1 M.Debido a su gran volumen, el electrodo de referencia estándar no es práctico para trabajar con ISFETs. Por ello se ha estudiado la realización de medidas diferenciales utilizando además del MEMFET de potasio, un ISFET de referencia (REFET) y el pseudo electrodo de platino integrado en el dispositivo permitiendo así la substitución del electrodo de referencia. El REFET se ha fabricado depositando una membrana polimérica de PVC inerte. Para mejorar la adherencia de la membrana a la superficie del REFET se ha realizado un proceso de silanización de la superficie, consistente en modificar químicamente la superficie del dieléctrico, de modo que se crean enlaces mediante los cuales la membrana queda bien adherida al dispositivo.Se ha caracterizado también el sensor de temperatura basado en una resistencia de platino integrado en la aguja. Los resultados obtenidos son muy lineales y repetitivos, con un valor del coeficiente de temperatura de la resistencia TRC de 26873 ppm/C.En la segunda parte de la tesis, se han desarrollado microelectrodos de estado sólido sensibles al ión hidrógeno en forma de aguja de silicio, basados en membranas poliméricas, utilizando como ionóforos el Chromoionoforo I (ETH 5294) y el Tri-n-dodecilamino (TDDA). Se ha depositado sobre los microelectrodos de platino un nuevo material polimérico conductor; el polipirrol dopado con el anión cobaltabisdicarballuro [3,3'-Co(1,2-C2B9H11)2]- mediante la técnica de electropolimerización. Este polímero actúa como capa intermedia entre el platino y la membrana. El empleo de esta etapa intermedia aumenta considerablemente la adherencia de la membrana PVC sobre la superficie del transductor y por tanto el tiempo de vida.Las características de respuesta de los microelectrodos son muy satisfactorias. Los dispositivos presentan una sensibilidad nernstiana en un rango de respuesta amplio (pH 3.5-11.0). Los coeficientes de selectividad potenciometricos obtenidos ponen de manifiesto la buena selectividad de los microelectrodos al ión hidrógeno en presencia de iones como potasio, sodio y litio.La ultima parte de este trabajo ha sido dirigida a la búsqueda de soluciones a dificultades que han sido encontradas en la utilización química de los MEMFETs sensibles al ión K+. En este sentido, se ha estudiado la modificación del óxido de silicio utilizado en la puerta del ISFET con el fin de variar su selectividad a iones específicos. Para ello se han fabricado estructuras capacitivas sensibles al ión potasio utilizando membranas inorgánicas basadas en la técnica de implantación iónica del ión aluminio y potasio en el oxido de silicio. Las estructuras han sido caracterizadas mediante la técnica capacidad-tensión (C-V) a alta frecuencia. Las características de respuesta obtenidas tanto en cuanto a sensibilidad como a selectividad han sido aceptables y comparables con las halladas en la bibliografía. / The thesis work has been focused on the development and the study of chemical multi-sensors based on silicon for biomedical applications. The work is divided in three parts:In the first part we fabricated sensors based on ion-sensitive field-effect transistors (ISFET). The device has the form of a needle and includes two ISFET sensors, a platinum pseudo-reference electrode and a temperature sensor based on a platinum resistor. The ISFETs have been characterised both electrically as MOSFET transistors and chemically as pH sensors with good results, thus demonstrating the viability of the fabrication technologies.Potassium selective MEMFET devices have been obtained by solvent-casting a poly(vinyl chloride) (PVC) plasticized potassium-sensitive membrane, containing valinomycin as ionophore, on the insulator gate. Linear responses have been obtained in a range of K+ activity between 10-4 M and 10-1 M approximately, with an almost Nerntsian sensitivity (50 ± 2 mV per decade).To make useful measurements with ISFETs in their final application, the use of conventional reference electrodes, which are big and fragile, should be avoided. This can be done if a differential setup is used, with two ISFETs that show different sensitivities to the measuring ion. In that case, a metallic quasi-reference electrode can be used. The electrical potential at the electrode-electrolyte interface is unstable, but it is measured by the differential ISFET pair as a common mode voltage and is eliminated. For the differential measurement one of the ISFETs has to be made insensitive to the measuring ion (reference-ISFET or REFET). In this work we used the platinum pseudo electrode integrated in the device. The REFET has been fabricated by depositing a polymeric PVC inert membrane. To improve the adherence of the membrane to the surface of the REFET, a surface functionalization process has been realized.The temperature sensor based on a platinum resistance integrated in the needle has been also characterized. The response of the resistance with the temperature is highly linear and repetitive with a resistance temperature coefficient of 26873 ppm/C.In the second part of the work, we have developed hydrogen selective solid state microelectrodes based on silicon needle. The microelectrodes are based on an hydrogen selective PVC membrane containing either Chromoionophore I (ETH 5294) or Tri-n-dodecylamine (TDDA) ionophores. A novel electrodeposited conductive polymer, Polypyrrole (PPy) doped with Cobaltabis(dicarbollide) ions ([3.3-Co(1.2C2B9H11)2]), has been used as a solid internal contact layer between the solid surface (Pt) and the polymeric sensitive membrane. The presence of this polypyrrole layer greatly increases the stability of the microelectrodes.The potenciometric response characteristics of the microelectrodes are very satisfactory. The devices exhibited excellent selectivity to Hydrogen against common interfering cations, as potassium, sodium and lithium, in background solutions. The pH response shows also a good linearity in a wide pH range (3.5-11.0), with Nernstian slopes.The last part of this work has been directed to the research of solutions to the difficulties that have been found in the chemical utilization of the potassium sensitive MEMFETs. We have studied the modification of the silicon dioxide on the ISFET gate to change its selectivity to specific ions. In this way we have obtained potassium-sensitive capacitive structures by ion implantation of K+ and Al+ ions into silicon dioxide on silicon with low energy in order to reduce the damage to the substrate during the process of implantation. As this method is compatible with the standard CMOS process, these results can be considered as promising for its application to the production of ISFET devices sensitive to potassium. The structures have been characterized by means of the capacity-tension (C-V) method at high frequency. The characteristics of response obtained (sensibility and selectivity) have been acceptable and comparable with those found in the bibliography.

In this thesis, the a-PMT (amorphous lead magnesium titanate) membranes have been prepared by sol-gel technique as H+ ion sensitive layers. The C-V measurements of the a-PMT/SiO2/Si EIS structures prepared by spin-on coating are used for examining the fabrication parameters and sensing properties. There exhibits the quasi-Nerstain response of 55¡V59 mV/pH in the range of pH 2¡V12, fabricated with the Mg-modified content of 4 mole%, the firing temperature of about 400 ¢J and the thickness of about 0.5

In this thesis, the aluminum nitride (AlN) thin film was selected as a sensing membrane for the H+ ion-sensitive field-effect transistor (ISFET). The AlN thin films were prepared by a rf sputtering technology on the reference electrode/electrolyte /AlN /SiO2/p-Si/Al structure. The capacitance-voltage (C-V) measurement was used to detect the H+ ion concentration and the C-V characteristic curves were obtained in the different pH buffer solutions. On the other hand, AlN thin films were also prepared on the double layer structure of AlN/SiO2 gate ISFET devices. After packaging, the current-voltage (I-V) measurement with a PID temperature controller was utilized to measure a series of the I-V characteristic curves. The threshold voltage can be obtained to evaluate the pH sensitivity in the different pH buffer solutions. Additionally, the effects of non-ideal factors, such as temperature effect, drift and hysteresis phenomenon on the characteristics of the ISFET are also measured, analyzed and compared with other sensing materials. According to the experimental results, it can be found that the ISFET based on aluminum nitride thin film has a superior high pH sensitivity of approximately 50~58 mV/pH at 25¢J. The drift and hysteresis are dependent on the H+ ion concentration in pH=1~11, in which the drift rate increases with the pH value increased and the hysteresis magnitude depends on the measuring time and route. It is found that the hysteresis widths measured in pH=7®3®7®11®7 cycle at 960s, 1920s and 3840s loop time are 1.0, 1.5 and 4.5 mV, respectively. When the temperature effect was considered, it was found that the ISFET could be operated at 5~65¢J, in which, the pH sensitivity increased as the ambient temperature increased with the temperature coefficient of sensitivity of about 0.13 mV/pH¢J. In addition, the output voltage of AlN pH-ISFET can be obtained by a constant current constant voltage (CCCV) read out circuit with a fairly linear response, stability and reproducibility in the pH measuring cycle. From the characteristics mentioned above, the AlN thin film can be as a sensing membrane for pH-ISFET applications.

Hydrogen ion-sensitive field effect transistor with sol-gel-derived La-modified lead titanate gate Department of Electrical Engineering, National Sun Yat-Sen University *Jen-Fu Su **Ying-Chung Chen Abstract In this thesis the amorphous lead lanthanum titanate (Pb1-xLaxTi1-x/4O3, PLT) membrane has been prepared by sol-gel method as a novel pH-sensitive layer. The lead lanthanum titanate membrane was directly deposited on the SiO2(1000Å)/p-Si substrate by spin-on coating to form the PLT/SiO2/Si EIS structure. The C-V measurement was used for examining the fabrication parameters and sensing properties. Moreover, the PLT membrane was grown onto the SiO2 gate ISFET as the PLT/SiO2 gate ISFET. The electrical properties with the different parameter conditions can be obtained by the I-V measurement. Experimental results show that the fabrication parameters and characteristics of the PLT membrane are determined at the La-modified content about 3 mol% and the firing temperature of 400¢J via the EIS structure. There exhibits the pH response of about 44-52 mV/pH in the range of pH 2-12. Furthermore, the nonideal factors, such as drift of 0.1-0.3 mV/h, hysteresis of 2-13 mV and lifetime decay of about 72 mV/pH-day, can be also obtained via the I-V properties of the ISFET. Finally, the hardware architecture of pH measuring system has been built up. The system makes use of constant current and voltage bias technique to ensure that the variations of the output voltage can give directly the variations of pH value. For the purpose of achieving the function of data calibration and driving the liquid crystal display (LCD), the 8051 microprocessor is employed. Keywords: ISFET, Sol-gel, Lead lanthanum titanate, Drift, Hysteresis, pH meter * Student ** Advisor

abstract: The past two decades have been monumental in the advancement of microchips designed for a diverse range of medical applications and bio-analysis. Owing to the remarkable progress in micro-fabrication technology, complex chemical and electro-mechanical features can now be integrated into chip-scale devices for use in biosensing and physiological measurements. Some of these devices have made enormous contributions in the study of complex biochemical processes occurring at the molecular and cellular levels while others overcame the challenges of replicating various functions of human organs as implant systems. This thesis presents test data and analysis of two such systems. First, an ISFET based pH sensor is characterized for its performance in a continuous pH monitoring application. Many of the basic properties of ISFETs including I-V characteristics, pH sensitivity and more importantly, its long term drift behavior have been investigated. A new theory based on frequent switching of electric field across the gate oxide to decrease the rate of current drift has been successfully implemented with the help of an automated data acquisition and switching system. The system was further tested for a range of duty cycles in order to accurately determine the minimum length of time required to fully reset the drift. Second, a microfluidic based vestibular implant system was tested for its underlying characteristics as a light sensor. A computer controlled tilt platform was then implemented to further test its sensitivity to inclinations and thus it‟s more important role as a tilt sensor. The sensor operates through means of optoelectronics and relies on the signals generated from photodiode arrays as a result of light being incident on them. ISFET results show a significant drop in the overall drift and good linear characteristics. The drift was seen to reset at less than an hour. The photodiodes show ideal I-V comparison between photoconductive and photovoltaic modes of operation with maximum responsivity at 400nm and a shunt resistance of 394 MΩ. Additionally, post-processing of the tilt sensor to incorporate the sensing fluids is outlined. Based on several test and fabrication results, a possible method of sealing the open cavity of the chip using a UV curable epoxy has been discussed. / Dissertation/Thesis / M.S. Electrical Engineering 2011

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Disponível o modelo em http://biblioteca.ufam.edu.br/servicos/teses-e-dissertacoes Dúvidas: ddbc@ufam.edu.br on 2018-10-19T12:54:42Z (GMT) / Submitted by Luciano Silva (lucianonilx@gmail.com) on 2018-10-19T15:23:11Z No. of bitstreams: 3 DISSERTAÇÃO - Luciano Lourenço.pdf: 3846130 bytes, checksum: 070519d3c19c8e9f1cdb22092cea3b5f (MD5) FOLHA DE APROVAÇÃO - Luciano Lourenço.pdf: 334305 bytes, checksum: aad04436441f1cf1af8fdb9bd5b6c694 (MD5) CARTA DE ENCAMINHAMENTO - LUCIANO LOURENÇO.pdf: 476516 bytes, checksum: 794b5fc4803231de174a7cc3b79d6f55 (MD5) / Approved for entry into archive by PPGEE Engenharia Elétrica (mestrado_engeletrica@ufam.edu.br) on 2018-10-22T11:50:50Z (GMT) No. of bitstreams: 3 DISSERTAÇÃO - Luciano Lourenço.pdf: 3846130 bytes, checksum: 070519d3c19c8e9f1cdb22092cea3b5f (MD5) FOLHA DE APROVAÇÃO - Luciano Lourenço.pdf: 334305 bytes, checksum: aad04436441f1cf1af8fdb9bd5b6c694 (MD5) CARTA DE ENCAMINHAMENTO - LUCIANO LOURENÇO.pdf: 476516 bytes, checksum: 794b5fc4803231de174a7cc3b79d6f55 (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2018-10-22T18:01:03Z (GMT) No. of bitstreams: 3 DISSERTAÇÃO - Luciano Lourenço.pdf: 3846130 bytes, checksum: 070519d3c19c8e9f1cdb22092cea3b5f (MD5) FOLHA DE APROVAÇÃO - Luciano Lourenço.pdf: 334305 bytes, checksum: aad04436441f1cf1af8fdb9bd5b6c694 (MD5) CARTA DE ENCAMINHAMENTO - LUCIANO LOURENÇO.pdf: 476516 bytes, checksum: 794b5fc4803231de174a7cc3b79d6f55 (MD5) / Made available in DSpace on 2018-10-22T18:01:03Z (GMT). No. of bitstreams: 3 DISSERTAÇÃO - Luciano Lourenço.pdf: 3846130 bytes, checksum: 070519d3c19c8e9f1cdb22092cea3b5f (MD5) FOLHA DE APROVAÇÃO - Luciano Lourenço.pdf: 334305 bytes, checksum: aad04436441f1cf1af8fdb9bd5b6c694 (MD5) CARTA DE ENCAMINHAMENTO - LUCIANO LOURENÇO.pdf: 476516 bytes, checksum: 794b5fc4803231de174a7cc3b79d6f55 (MD5) Previous issue date: 2018-06-29 / In recent decades, special attention has been paid to the study of silicon-based biosensors in the field of bioanalytical applications, due to their favorable operating characteristics, which include: good sensitivity, processing speed, miniaturization and low cost. Among these, the Ion Sensing Field Effect Transistor (ISFET) is one of the most popular biosensors and is regarded as the first miniaturized silicon-based chemical sensor. The ISFET conventionally used as a pH sensor has been widely used to measure the concentration of hydrogen ions of a substance (H + or OH-) [1] [2]. This work presents an alternative model for ISFET sensors based on the simulation limitations of the classic model presented by Martinoia [3] [4]. The alternative model can be used in both permanent and transient regime simulations, including also the effect of temperature, where it is desired to investigate the electrical signal resulting from a reading circuit used for the initial treatment of the signal transduced by a pH sensitive ISFET sensor. The electrochemical stage of an ISFET is responsible for emulating the device's ion sensitivity. The alternative model is able to represent this stage through a simpler circuit topology than those found in the literature, without loss of generality. The simulation results using the proposed ISFET model are compatible with those presented in the literature, thus affirming its effectiveness. This work also presents a signal conditioning circuit for ISFET sensors sensitive to pH with temperature compensation. As compared to the conventional circuit topologies found in the literature, besides the temperature effect compensation, the proposed analog interface has at least two advantages. The first is related to simplicity and, consequently, to the reduced size of the circuit; the second is the additional gain conferred to the sensor output signal. Its performance was investigated through simulations performed in SPICE (Simulation Program with Integrated Circuit Emphasys) simulator using the BSIM3v3 models. The BSIM3 (Berkeley Short Channel Insulated field effect transistor Model) models are public models developed at the University of Berkeley, California; such models are widely used in simulations of analog and digital circuits that use MOS devices of submicron dimensions. The conventional reading circuit topologies for ISFET sensors do not confer sensitivity gain and have their output limited to the sensitivity of the transducer element, as predicted by the Nernst model [2] and observed by Martinoia [3] [4]. The simulation results show that in its basic design, the circuit topology proposed in this work grants additional gains to the sensor output signal, increasing its sensitivity up to forty times the theoretical limit of Nernst; in an alternative design the gain granted reaches up to ten times the sensor limit, but with the compensation of the effect of the temperature. / Nas últimas décadas, uma atenção especial vem sendo dada ao estudo de biosensores baseados em silício no campo de aplicações bioanalíticas, devido as suas características favoráveis de operação que incluem: boa sensibilidade, velocidade de processamento, miniaturização e baixo custo. Entre estes, o Transistor de Efeito de Campo Sensível a Íons (ISFET) é um dos biosensores mais populares e é tido como o primeiro sensor químico à base de silício miniaturizado. O ISFET utilizado convencionalmente como sensor de pH, tem sido amplamente utilizado para medir a concentração de íons de hidrogênio de uma substância (H+ ou OH-) [1] [2]. Este trabalho apresenta um modelo alternativo para sensores ISFET com base nas limitações de simulação do modelo clássico apresentado por Martinoia [3] [4]. O modelo alternativo pode ser empregado tanto em simulações de regime permanente quanto transientes, incluindo também o efeito da temperatura, onde se deseja investigar o sinal elétrico resultante de um circuito de leitura utilizado para o tratamento inicial do sinal transduzido por um sensor ISFET sensível a pH . O estágio eletroquímico de um ISFET é responsável por emular a sensibilidade a íons do dispositivo. O modelo alternativo é capaz de representar esse estágio por meio de uma topologia de circuito mais simples do que as encontradas na literatura, sem perda de generalidade. Os resultados de simulação empregando o modelo de ISFET proposto são compatíveis com os apresentados na literatura, afirmando assim sua eficácia. Este trabalho apresenta ainda um circuito de condicionamento de sinais para sensores ISFET sensíveis a pH com compensação do efeito da temperatura. Quando comparada às topologias de circuito convencionais encontradas na literatura, além da compensação do efeito de temperatura, a interface analógica proposta apresenta pelo menos duas vantagens. A primeira está relacionada à simplicidade e, consequentemente, ao tamanho reduzido do circuito; o segundo é o ganho adicional conferido ao sinal de saída do sensor. Seu desempenho foi investigado através de simulações realizadas em simulador SPICE (Simulation Program with Integrated Circuit Emphasys) utilizando os modelos BSIM3v3. Os modelos BSIM3 (Berkeley Short channel Insulated field effect transistor Model) são modelos públicos desenvolvidas na Universidade de Berkeley, Califórnia; tais modelos são amplamente utilizados em simulações de circuitos analógicos e digitais que se utilizam de dispositivos MOS de dimensões submicrométricas. As topologias de circuitos de leitura convencionais para sensores ISFET não conferem ganho de sensibilidade e têm sua saída limitada à sensibilidade do elemento transdutor, conforme previsto pelo modelo de Nernst [2] e observado por Martinoia [3] [4]. Os resultados de simulação mostram que em sua concepção básica, a topologia de circuito proposta neste trabalho concede ganhos adicionais ao sinal de saída do sensor, aumentando sua sensibilidade em até quarenta vezes o limite teórico de Nernst; numa concepção alternativa o ganho concedido chega a até dez vezes o limite do sensor, mas com a compensação do efeito da temperatura.

Neste trabalho é apresentada a análise de técnicas para a integração de ISFETs (Ion Selective Field Effect Transitors), através do método de montagem por viragem (Flip-chip) usando pasta de solda livre de chumbo e epóxi condutivo de prata, com o objetivo de permitir sua aplicação em Microssistemas de Análise Total (µTAS). Para os testes de integração foram construídas estruturas em dois substratos, o FR-4, pelo método de ligação por fios (wire bonding), e o LTCC, que pode ser aplicado na construção de µTAS. Como os terminais de contato do ISFET tem seu acabamento superficial em alumínio não é possível realizar a montagem por viragem utilizando equipamentos SMT, sendo necessários processos intermediários. Dois processos que permitem o uso de equipamentos SMT foram aplicados: a remetalização, onde camadas de níquel e ouro são depositadas sobre o alumínio do terminal de contato, através do banho químico eletrolítico sem eletrodo (Electroless), e protuberâncias de solda (stud ou ball bumps), que são ligadas ao alumínio do terminal de contato pelo processo conhecido como Stud Ball Bumping (SBB). Na integração do ISFET foi feita a selagem dos terminais de contato e a abertura de uma janela que permite o contato da área ativa (região de porta) do ISFET com as soluções a serem analisadas. A selagem dos terminais de contato foi feita com o fotoresiste SU-8, e a abertura da área ativa foi feita diretamente sobre os substratos de FR-4 e LTCC. Ambos processos apresentaram soldabilidade com a pasta de solda apresentando ponto de refusão em torno de 250°C, indicando que equipamentos SMT podem ser aplicados na montagem por viragem. Verificou-se que o epóxi condutivo de prata foi curado a 100°C por uma hora e também pode ser aplicado na integração do ISFET. Por fim o SU-8 usado na selagem apresentou uma boa adesão aos substratos de FR-4 e LTCC, sendo curado na mesma etapa térmica da pasta de solda e/ou epóxi condutivo de prata ou após estes processos a 150°C por trinta minutos. / In this work is shown the analysis of integration techniques of ISFET (Ion Selective Field Effect Transitor) through the Flip-chip method using lead-free solder paste and silver conductive epoxy, in order to allow its application in Micro Total Analysis System (µTAS). For integration tests two substrates have been made, the FR-4, as already used in the integration of the ISFET, but assembled through wire bonding method, and the LTCC that can be applied in the construction of µTAS. As the ISFET bonding pads has its surface finish in aluminum is not possible assembly through flip-chip method using SMT equipments, requiring intermediate processes. Two process that allow the use of SMT equipment were applied: the remetallization, where nickel and gold layers are deposited on the aluminum bonding pads, through the Electroless chemical baths, and stud or ball bumps, which are connected to bonding pads of aluminum by the process known as Stud Ball Bumping (SBB). In the ISFET integration should be made a seal in the bonding pads and a window that allows the contact of the active area (gate region) of ISFET with the solutions to be analyzed. The sealing of the bonding pads has been made with the photoresist SU-8 and the window of active area were made directly on the FR-4 and LTCC substrates. Both processes presented the solderability with the solder paste reflowed at 250°C, indicating that SMT equipments may be applied to the assembly through flip-chip method, the silver conductive epoxy was cured at 100°C for one hour and can also be applied in ISFET integration. Finally the SU-8 used to sealing have showed a good adherence to the FR-4 and LTCC substrates, being cured in the same thermal step of solder paste and/or silver conductive epoxy or after these processes at 150°C for thirty minutes.

Neste trabalho é apresentada a análise de técnicas para a integração de ISFETs (Ion Selective Field Effect Transitors), através do método de montagem por viragem (Flip-chip) usando pasta de solda livre de chumbo e epóxi condutivo de prata, com o objetivo de permitir sua aplicação em Microssistemas de Análise Total (µTAS). Para os testes de integração foram construídas estruturas em dois substratos, o FR-4, pelo método de ligação por fios (wire bonding), e o LTCC, que pode ser aplicado na construção de µTAS. Como os terminais de contato do ISFET tem seu acabamento superficial em alumínio não é possível realizar a montagem por viragem utilizando equipamentos SMT, sendo necessários processos intermediários. Dois processos que permitem o uso de equipamentos SMT foram aplicados: a remetalização, onde camadas de níquel e ouro são depositadas sobre o alumínio do terminal de contato, através do banho químico eletrolítico sem eletrodo (Electroless), e protuberâncias de solda (stud ou ball bumps), que são ligadas ao alumínio do terminal de contato pelo processo conhecido como Stud Ball Bumping (SBB). Na integração do ISFET foi feita a selagem dos terminais de contato e a abertura de uma janela que permite o contato da área ativa (região de porta) do ISFET com as soluções a serem analisadas. A selagem dos terminais de contato foi feita com o fotoresiste SU-8, e a abertura da área ativa foi feita diretamente sobre os substratos de FR-4 e LTCC. Ambos processos apresentaram soldabilidade com a pasta de solda apresentando ponto de refusão em torno de 250°C, indicando que equipamentos SMT podem ser aplicados na montagem por viragem. Verificou-se que o epóxi condutivo de prata foi curado a 100°C por uma hora e também pode ser aplicado na integração do ISFET. Por fim o SU-8 usado na selagem apresentou uma boa adesão aos substratos de FR-4 e LTCC, sendo curado na mesma etapa térmica da pasta de solda e/ou epóxi condutivo de prata ou após estes processos a 150°C por trinta minutos. / In this work is shown the analysis of integration techniques of ISFET (Ion Selective Field Effect Transitor) through the Flip-chip method using lead-free solder paste and silver conductive epoxy, in order to allow its application in Micro Total Analysis System (µTAS). For integration tests two substrates have been made, the FR-4, as already used in the integration of the ISFET, but assembled through wire bonding method, and the LTCC that can be applied in the construction of µTAS. As the ISFET bonding pads has its surface finish in aluminum is not possible assembly through flip-chip method using SMT equipments, requiring intermediate processes. Two process that allow the use of SMT equipment were applied: the remetallization, where nickel and gold layers are deposited on the aluminum bonding pads, through the Electroless chemical baths, and stud or ball bumps, which are connected to bonding pads of aluminum by the process known as Stud Ball Bumping (SBB). In the ISFET integration should be made a seal in the bonding pads and a window that allows the contact of the active area (gate region) of ISFET with the solutions to be analyzed. The sealing of the bonding pads has been made with the photoresist SU-8 and the window of active area were made directly on the FR-4 and LTCC substrates. Both processes presented the solderability with the solder paste reflowed at 250°C, indicating that SMT equipments may be applied to the assembly through flip-chip method, the silver conductive epoxy was cured at 100°C for one hour and can also be applied in ISFET integration. Finally the SU-8 used to sealing have showed a good adherence to the FR-4 and LTCC substrates, being cured in the same thermal step of solder paste and/or silver conductive epoxy or after these processes at 150°C for thirty minutes.