Abstract: A wet etch bath (61) holds a wet etchant (52) for etching a dielectric over a semiconductor substrate. The wet etch bath (61) has a tub (63) separated from a reservoir (64) by a wall (65). The tub (63) is filled with the wet etchant (52) to a height of the wall (65). The reservoir (64) is filled with the wet etchant (52) to a height less than the height of the wall. A pump (66) coupled to the reservoir (64) pumps the wet etchant (52) through an osmotic membrane degasifier (69) to the tub (63). Adding the wet etchant (52) to the tub (63) causes the wet etchant (52) to cascade over the wall (65) back to the reservoir (64). The osmotic membrane degasifier (69) reduces a concentration of a reactive agent in the wet etchant (52).

Abstract: A sacrificial oxide etching solution of carboxylic acid and HF having a high etch selectivity for silicon oxide relative to polysilicon, metal, and nitride. The solution is useful in the fabrication of microstructures having integrated electronics on the same chip. A carboxylic acid anhydride can be added to this solution to substantially remove all free water so that the etch selectivity to metal is improved. One specific solution is formed by mixing acetic acid, acetic anhydride, and aqueous HF.

Abstract: A wet etching process (10) etches sacrificial oxide on a substrate without damaging a polycrystalline silicon structure on the substrate. The etching process (10) includes dipping the substrate in a surfactant (11), submerging a portion of the substrate in a recirculating bath of the etchant while injecting an inert gas into the etchant (12) to purge the etchant of oxygen, rinsing the substrate in deionized water (14), submerging a portion of the substrate in a hydrogen peroxide solution (15), rinsing the substrate for a second time (17), and drying the substrate in isopropyl alcohol vapor (18). The inert gas injected into the etchant displaces oxygen dissolved in the etchant and protects the polycrystalline silicon structure from being etched.

Abstract: A fuel system for an internal combustion engine includes a pump/injector having an actuating winding to which power is supplied by a first electronic means. A first control signal is supplied by a second electronic means to energize the winding and a second control signal is supplied by a third electronic means to de-energize the winding. The third electronic means calculates the time at which the winding should be de-energized to allow the piston in the pump to draw in the required volume of fuel, the second electronic means causing delivery of fuel when the required volume of fuel has been drawn into the pumping chamber of the pump.

Abstract: The output of a transducer is passed to an electrical circuit for supply to a fuel control network. In order to check the output of the transducer the output of the electrical circuit is sampled in a sample circuit when the movement of the member associated with the transducer is a known value. The signal from the sample circuit is compared in a comparator with a reference signal. Any difference is passed to a gain determining circuit which calculates a new gain value for a variable gain amplifier in the electrical circuit. The value of the gain is retained in a holding circuit and supplied to the amplifier until further adjustment is required.

Abstract: A fuel system for supplying fuel to an engine includes a nozzle positioned to direct fuel into a combustion chamber and an electromagnetically operable pump for supplying fuel to the nozzle. A first electronic means supplies power to a winding of the pump to cause delivery of fuel and holds the pumping piston of the pump until it is required to fill the pumping chamber of the pump. A second electronic means partly energizes the winding or another winding when the required amount of fuel has flowed into the pumping chamber, to hold the piston against movement.