MOS Integrated circuits with implanted resistor elements

Claim 1

A method of making resistor elements in N-channel, silicon-gate MOS integrated circuit devices, comprising the steps of: growing a thin silicon oxide coating on a surface of a monocrystalline silicon slice containing a first conductivity type determining impurity; covering the thin silicon oxide coating with a thin layer of silicon nitride; removing the silicon nitride coating in a pattern to expose selected resistor areas; implanting a second conductivity-type determining impurity opposite the first type into a shallow surface-adjacent region of the silicon in said resistor areas by exposing the slice to an ion beam, such implanting being done through said thin silicon oxide coating; subjecting the slice to an elevated temperature in an inert atmosphere to raise the concentration of the first impurity below said surface-adjacent region; oxidizing the slice at an elevated temperature for a time exceeding that used in the prior step to create a thick silicon oxide coating in said exposed areas and covering the resistor areas; forming an electrical connection to each of a plurality of spaced portions of the implanted region in said resistor area; removing the remaining silicon nitride from the surface of the slice; and forming MOS transistors on said slice by diffusing or implanting into the slice said second conductivity-type determining impurity creating regions in the slice continguous to said resistor areas.

Claim 2

A method of making resistor elements in N-channel, silicon-gate MOS integrated circuit devices, comprising the steps of: growing a thin silicon oxide coating on a surface of a monocrystalline silicon slice containing a first conductivity type determining impurity; covering the thin silicon oxide coating with a thin layer of silicon nitride; removing the silicon nitride coating in a pattern to expose selected resistor areas; implanting a second conductivity-type determining impurity opposite the first type into a shallow surface-adjacent region of the silicon in said resistor areas by exposing the slice to an ion beam, such implanting being done through said thin silicon oxide coating; subjecting the slice to an elevated temperature in an inert atmosphere to raise the concentration of the first impurity below said surface-adjacent region; oxidizing the slice at an elevated temperature for a time exceeding that used in the prior step to create a thick silicon oxide coating in said exposed areas and covering the resistor areas; forming an electrical connection to each of a plurality of spaced portions of the implanted region in said resistor area; removing the remaining silicon nitride from the surface of the slice; and forming MOS transistors on said slice by diffusing or implanting into the slice said second conductivity-type determining impurity creating regions in the slice continguous to said resistor areas.

Claim 8

A method making resistor elements in a silicon slice in manufacture of MOS integrated circuits of the type having MOS transistors, comprising: implanting conductivity-type determining impurity material in selected resistor areas at the surface of the silicon slice; and thereafter oxidizing selected regions of said surface by heating the slice in an oxidizing atmosphere, producing thick field oxide which covers said selected resistor areas, and forming said MOS transistors with gate oxide much thinner than the field oxide.

Claim 9

A method making resistor elements in a silicon slice in manufacture of MOS integrated circuits of the type having MOS transistors, comprising: implanting conductivity-type determining impurity material in selected resistor areas at the surface of the silicon slice; and thereafter oxidizing selected regions of said surface by heating the slice in an oxidizing atmosphere, producing thick field oxide which covers said selected resistor areas, and forming said MOS transistors with gate oxide much thinner than the field oxide.

Claim 12

A method of making a circuit element in a semiconductor integrated circuit, comprising the steps of: implanting conductivity-type determining impurity material in a selected area in a face of a semiconductor body to produce an implanted region of opposite conductivity-type from the bulk of the body; covering the face of the body with a thick oxide coating by heating in an oxidizing atmosphere, consuming the bulk of said region and driving said impurity material further into said face of the body, while masking contact areas on opposite ends of the selected area to prevent oxidation thereof; and introducing conductivity-type determining impurity into the contact areas to provide electrical connection to the circuit element.

Claim 13

A method of making a circuit element in a semiconductor integrated circuit, comprising the steps of: implanting conductivity-type determining impurity material in a selected area in a face of a semiconductor body to produce an implanted region of opposite conductivity-type from the bulk of the body; covering the face of the body with a thick oxide coating by heating in an oxidizing atmosphere, consuming the bulk of said region and driving said impurity material further into said face of the body, while masking contact areas on opposite ends of the selected area to prevent oxidation thereof; and introducing conductivity-type determining impurity into the contact areas to provide electrical connection to the circuit element.