Abstract: Methods, apparatus and chip fabrication techniques are described which provide electrostatic discharge (ESD) protection to ion-sensitive field effect transistor (ISFET) based devices used to selectively measure ions in a liquid. According to one aspect of the invention, an ESD protection circuit, made up of conventional protective elements, is integrated onto the same silicon chip on which the ISFET is formed, along with an interface that is in contact with the liquid being measured and which does not open up paths for D.C. leakage currents between the ISFET and the liquid. According to a preferred embodiment of the invention, a capacitor structure is used as the interface between the protection circuit and the liquid sample. Further aspects of the invention are directed to methods per se for providing ESD protection for ISFET sensors utilizing the interface means (e.g, capacitor structure) referred to hereinabove, and processes for fabricating the novel interface on a silicon wafer.

Abstract: Methods, apparatus and chip fabrication techniques are described which provide electrostatic discharge (ESD) protection to ion-sensitive field effect transistor (ISFET) based devices used to selectively measure ions in a liquid. According to one aspect of the invention, an ESD protection circuit, made up of conventional protective elements, is integrated onto the same silicon chip on which the ISFET is formed, along with an interface that is in contact with the liquid being measured and which does not open up paths for D.C. leakage currents between the ISFET and the liquid. According to a preferred embodiment of the invention, a capacitor structure is used as the interface between the protection circuit and the liquid sample. Further aspects of the invention are directed to methods per se for providing ESD protection for ISFET sensors utilizing the interface means (e.g, capacitor structure) referred to hereinabove, and processes for fabricating the novel interface on a silicon wafer.

Abstract: This invention provides a method for producing header mounted sensors, such as a chemically sensitive ISFET structures, which comprises steps which include providing a plurality of electrochemically sensitive ISFET sites on a semiconductor substrate with a source region, a drain region and an electrochemically sensitive gate region on the front of said substrate with contacts for said regions on the back of the substrate. A glass carrier, such as borosilicate glass is provided for the substrate. The carrier has a hole in it to maintain uncovered the contact areas of the ISFET sites and the carrier also has leads to provide electrical access to the area of the holes from the edges of the carrier. The substrate is electrostatically bonded to the glass carrier at the periphery of each of the ISFET sites and the boundaries of the individual ISFET sites are V-groove etched to form isolated individual silicon mesas each representing an individual ISFET structure.

Abstract: An electrostatically bonded capacitive pressure measuring transducer constructed with a silicon diaphragm member sandwitched between a top silicon support plate and a bottom silicon support plate each of which has a via hole extending therethrough, a thin layer of borosilicate glass interposed between the diaphragm and each of the support plates, a metallized deposit extending through the via holes and over a part of the surface of each of the glass layers opposite the diaphragm to form with the diaphragm two variable capacitors which will be electrically contacted by spring loaded plunger type contacts, and a layer of platinum silicide deposited on the top of the silicon diaphragm and the top of each of the silicon plates as an electrical contact coating providing a contact surface for the plunger type contacts.

Abstract: The structure consists of a substrate, a set of interdigitated electrodes deposited on the substrate surface. The electrode fingers have a period less than the substrate thickness. A first water permeable polymer film is deposited over the electrodes and a conductive mesh is formed over the first polymer film. A second polymer film is deposited over the mesh burying the mesh between the two polymer films. The spacing between openings of the mesh is less than the thickness of the second polymer film. The square of the sum of the two polymer film thicknesses is minimized so that the response time is minimized. The mesh conductivity is made greater than a minimum value so that the resistive component of the impedance is small compared with the capacitive impedance, and thus the device impedance is independent of any instabilities in the conductive mesh impedance.

Abstract: A capacitive pressure transducer whose diaphragm is formed of single crystal, highly doped silicon by etching in opposite sides the recesses which define the deflecting region of the diaphragm. This deflecting region serves as one electrode of the transducer. Two support plates of silicon are anodically bonded to opposite sides of the diaphragm along its periphery using thin layers of borosilicate glass to form with the etched recesses pressure receiving cavities. These thin layers of borosilicate glass are interposed between the diaphragm and a support plate, and extend over the entire surface of the support plate facing the diaphragm to provide for electrical isolation as well as the bonding between the diaphragm and the support plates. These layers of glass are made as thin as possible consistent with the need to maintain the stray capacitance below a certain value.

Abstract: There is provided an ISFET structure and a method for manufacturing that structure such that external electrical contact to the P+ source and drain regions is made through individual holes etched from the back to the source and drain regions with sidewall isolation being provided in the holes and metallization covering the surface of said sidewalls and extending to contact pads on the back of the ISFET.

Abstract: A thin film resistance thermometer is manufactured to have a predetermined temperature coefficient of resistance while minimizing the amount of metal in the film. The process involves the production of a metal film deposit on an insulating substrate such that the film deposited has a bulk coefficient substantially higher than the desired coefficient with the film being deposited to a thickness that produces the desired coefficient.

Abstract: A thin film resistance thermometer is manufactured to have a predetermined temperature coefficient of resistance while minimizing the amount of metal in the film. The process involves the production of a metal film deposit on an insulating substrate such that the film deposited has a bulk coefficient substantially higher than the desired coefficient with the film being deposited to a thickness that produces the desired coefficient.

Abstract: A resistance thermometer probe assembly is constructed by locating a header assembly in the end of a cylindrical sleeve. The header is constructed as a stack of discs. The disc exposed to the environment is of stainless steel and the disc supporting the thin film resistance thermometer chip is of ceramic. A copper disc is brazed between the ceramic and the stainless steel to accommodate the different thermal coefficients of expansion. Nail-head pins are brazed to a thick film deposit on the exposed face of the ceramic disc and the resistance thermometer chip is connected electrically between the pins.