General Signal Corporation

Paul M Kroninger, Jr

Paul J Freud

Ronald D Baxter

Paul B Binder

Dean P Updike

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. After formation of the individual mesas a passivation coating is deposited over the front of the substrate in a manner which will not obviate the chemical sensitivity of the gate region. There is then provided electrical contact from the contact areas of the ISFET to the metallized electrical leads of the carrier and the wafer is then diced at the site boundaries to produce individual chemically sensitive ISFET structures.

Header mounted chemically sensitive ISFET and method of manufacture

A differential pressure transducer assembly for measuring flow in dirty and solids bearing fluids utilizes small barrier diaphragms located at the pressure taps of a flow measuring restriction. The barrier diaphragms are of minimum size and minimum thickness with a minimum volumetric compliance and are connected to a pressure receiving body by equal length capillaries of minimum i.d. A measuring transducer with a diaphragm having low volumetric displacement for measured differential pressures and having minimum volume diaphragm cavities is connected to the capillaries by equal and minimum volume cavities in the pressure receiving body. The pressure receiving body cavities on both the high pressure side and the low pressure side incorporate close tolerance inserts of material having a low thermal expansion coefficient when compared to that of the pressure receiving body, so that with increases in temperature the volumes of the cavities, which are minimized as much as possible, will increase just enough to match the increase in volume of the fill fluid which fills the cavities and capillaries.

Remote probe differential pressure transducer

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.

Electrical contact coating for silicon pressure transducers

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. The transducer is mounted to a pressure receiving assembly by using a silicon stub having a passage for communicating one pressure to be measured to the transducer. The stub is joined at one end to the transducer by anodic bonding using a thin layer of borosilicate glass. A weldable tube is attached to the stub. This tube is long with respect to the stub and has a reduced diameter at one end which fits into the passage of the stub. The reduced diameter is kept at a minimum. The tube is welded to the pressure receiving body at its end to provide mechanical isolation for the transducer.

Pressure transducer and mounting

A bulkhead feedthrough for capacitive pressure transducers including a feedthrough body portion welded in a cylindrical opening in a pressure receiving body in which the transducer is mounted. The feedthrough body provides a pressure seal for the transducer cavity and carries conducting rods in holes in the body. The rods are insulated from the body and holes are drilled in the end of each rod from the transducer side to receive spring loaded plunger type contacts which are inserted in the holes so that the plunger protrudes to contact the transducer elements. The dimensions of the feedthrough body and the thermal coefficient of expansion are such that the space between the feedthrough body and the pressure receiving body varies with temperature changes so that the resulting volume changes are sufficient to compensate for the changes in volume of the silicone oil in the transducer cavities.

Electrical feedthrough means for pressure transducer

A capacitive pressure transducer utilizing a plate of electrically conductive semi-conductor material sandwiched between a pair of plates of inorganic electrically insulating material and electrostatically bonded thereto. A pair of concentric circular recesses are etched in the plates in such a way as to form cavities on opposing sides of the conductive plate and to define a diaphragm area on that plate. Apertures are drilled through the insulating plates to expose the cavities to the pressures to be measured. The surfaces of the insulating plates in the cavities have deposited on them electrically conductive surfaces which form capacitors with the diaphragm area on the conductive plate. A stress relief area is provided on the high pressure side surrounding the diaphragm area. In that stress relief area, the conductive plate is unrestrained by the adjacent insulating plate. Provision of this stress relief makes it possible to extend the pressure range of the transducer beyond the range which would normally be useful for the dimensions of the particular transducer.

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Harleysville, PA, United States of America

Paul M Kroninger, Jr