Method of integrated circuit fabrication

Claim 2

IN A METHOD FOR FABRICATING A SEMICONDUCTOR INTEGRATED CIRCUIT DEVICE INCLUDING A TRANSISTOR, COMPRISING THE STEP OF FORMING INTO THE SURFACE OF A BODY OF SEMICONDUCTIVE MATERIAL OF A FIRST CONDUCTIVITY TYPE A FIRST PATTERN COMPRISING A PLURALITY OF ZONES OF A SECOND CONDUCTIVITY TYPE, AND FORMING AN EPITAXIAL LAYER OF THE FIRST CONDUCTIVITY TYPE OVER THE SURFACE OF THE BODY THE IMPROVEMENT BEING THE STEPS OF: ION IMPLANTING INTO THE EPITAXIAL LAYER A SECOND PATTERN OF ZONE OF IMPURITIES OF THE SECOND CONDUCTIVITY TYPE REGISTERED WITH ZONES OF THE FIRST PATTERN; HEATING IN A MANNER SUFFICIENT TO DIFFUSE THE IMPURITIES THROUGH THE EXPITAXIAL LAYER AND SIMULTANEOUSLY TO OXIDIZE SELECTIVELY THE SURFACE OF THE EPITAXIAL LAYER ABOVE THE SECOND PATTERN OF IMPURITIES; ION IMPLANTING A BURIED BASE ZONE BENEATH AND SEPARATED FROM THE SURFACE OF THE EPITAXIAL LAYER; AND FORMING AN EMITTER ZONE EXTENDING INWARD FROM THE SURFACE OF THE EPITAXIAL LAYER TO THE BASE ZONE.

Claim 3

A method as recited in claim 1 wherein the second pattern zones of the second conductivity type are provided by: forming over the epitaxial layer a masking layer of a material capable of masking oxidation and etching selectively with respect to the oxide and to the semiconductor; forming through the masking layer the second pattern comprising a plurality of spaced voids registered with separate ones of the zones of the first pattern; ion implanting impurities of the second conductivity type into the areas beneath the voids of the second pattern; heating in an oxidizing atmosphere sufficient to cause impurities of the second pattern to penetrate essentially completely through the epitaxial layer and sufficient simultaneously to form oxide regions on the surface of the epitaxial layer selectively in the voids in the masking layer; and removing the masking layer by etching in a solution which substantially affects neither the selectively formed oxide nor the semiconductor material.

Claim 4

A method as recited in claim 1 further comprising: shaping the zones of the second pattern so separate zones of the second pattern form separate resistors in series with separate zones of the first pattern; and forming electrodes to contact separate zones of the second pattern so that greater resistance is obtained by placing an electrode at a greater distance from the serially connected zone of the first pattern.

Claim 5

A method as recited in claim 1 further comprising: forming completely through the epitaxial layer a plurality of oxide regions each of which laterally surrounds at least one zone of the first pattern and at least one zone of the second pattern and theReby laterally isolates said last-mentioned zones from the remainder of the epitaxial layer.

Claim 6

A method as recited in claim 1 further comprising: shaping separate zones of the second pattern to surround laterally at least one zone of the first pattern thereby isolating the portions of the epitaxial layer above said last-mentioned at least one zone from the remainder of the epitaxial layer.

Claim 7

A method as recited in claim 1 wherein the buried base zones and emitter zones are formed by: depositing an oxide layer containing impurities of the first conductivity type; forming a plurality of spaced voids to provide exposed regions of epitaxial layer above separate ones of the zones of the first pattern and above separate ones of the zones of the second pattern thereby producing a mask; heating the oxide layer sufficient that oxide layer impurities of the first conductivity type diffuse into those portions of the epitaxial layer essentially only underneath the remainder of the oxide layer and form a distribution of first conductivity type impurities whose concentration decreases with increasing distance into the epitaxial layer; ion implanting impurities of the first conductivity type into the epitaxial layer through the last mentioned spaced voids to form, over the zones of the first pattern, buried base zones having a distribution of first conductivity type impurities whose concentration first increases then decreases with increasing distance into the epitaxial layer; and introducing impurities of the second conductivity type through the last-mentioned spaced voids to form distributions of second conductivity type impurities whose concentration decreases with increasing distance into the epitaxial layer thereby producing emitter zones above the base zones and producing zones with improved ohmic contact characteristics above the second pattern zones.

Claim 8

A method as recited in claim 6 wherein the implantation of the base zones is sufficient that, at the distance into the epitaxial layer where the magnitude of the concentration of the implanted base impurity distribution has increased to at least 10 percent of its peak concentration, the concentration of the diffused first conductivity distribution is greater than the concentration of the implanted base impurity distribution.

Claim 9

A method as recited in claim 6 wherein the implantation of the base zones is sufficient that, at the distance into the epitaxial layer where the magnitude of the concentration of the implanted base impurity distribution has increased to at most 5 percent of its peak concentration, the concentration of the emitter impurity distribution is less than the concentration of the implanted base impurity distribution.

Claim 10

A method as recited in claim 6 wherein said epitaxial layer is of P-type conductivity silicon.

Claim 11

In a method for fabricating a semiconductor integrated circuit device including a transistor comprising the steps of forming into the surface of a body of semiconductive material of a first conductivity type a first pattern comprising a plurality of zones of a second conductivity type, and forming an epitaxial layer of the first conductivity type over the surface of the body, the improvement being the steps of: forming into the epitaxial layer a second pattern of zones of impurities of the second conductivity type registered with zones of the first pattern; depositing an oxide layer containing impurities of the first conductivity type; forming a plurality of spaced voids to provide exposed regions of epitaxial layer above separate ones of the zones of the first pattern and above separate ones of the zones of the second pattern thereby producing a mask; heating the oxide layer sufficient that oxide layer impurities of the first conductivity type diffuse into those portions of the epitaxial layer essentially only underneath the remainder of the oxide layer and form a distribution of first conductivity type impurities wHose concentration decreases with increasing distance into the epitaxial layer; ion implanting impurities of the first conductivity type into the epitaxial layer through the last mentioned spaced voids to form, over the zones of the first pattern, buried base zones having a distribution of first conductivity type impurities whose concentration first increases then decreases with increasing distance into the epitaxial layer; and introducing impurities of the second conductivity type through the last-mentioned spaced voids to form distributions of second conductivity type impurities whose concentration decreases with increasing distance into the epitaxial layer thereby producing emitter zones above the base zones and producing zones with improved ohmic contact characteristics above the second pattern zones.

Claim 12

In a method for fabricating a semiconductor integrated circuit device including a transistor comprising the steps of forming into the surface of a body of semiconductive material of a first conductivity type a first pattern comprising a plurality of zones of a second conductivity type, and forming an epitaxial layer of the first conductivity type over the surface of the body, the improvement being the steps of: forming into the epitaxial layer a second pattern of zones of impurities of the second conductivity type registered with zones of the first pattern; depositing an oxide layer containing impurities of the first conductivity type; forming a plurality of spaced voids to provide exposed regions of epitaxial layer above separate ones of the zones of the first pattern and above separate ones of the zones of the second pattern thereby producing a mask; heating the oxide layer sufficient that oxide layer impurities of the first conductivity type diffuse into those portions of the epitaxial layer essentially only underneath the remainder of the oxide layer and form a distribution of first conductivity type impurities wHose concentration decreases with increasing distance into the epitaxial layer; ion implanting impurities of the first conductivity type into the epitaxial layer through the last mentioned spaced voids to form, over the zones of the first pattern, buried base zones having a distribution of first conductivity type impurities whose concentration first increases then decreases with increasing distance into the epitaxial layer; and introducing impurities of the second conductivity type through the last-mentioned spaced voids to form distributions of second conductivity type impurities whose concentration decreases with increasing distance into the epitaxial layer thereby producing emitter zones above the base zones and producing zones with improved ohmic contact characteristics above the second pattern zones.

Claim 13

A method as recited in claim 10 wherein the second pattern zones of the second conductivity type are provided by: forming over the epitaxial layer a masking layer of a material capable of masking oxidation and etching selectively with respect to the oxide and to the semiconductor; forming through the masking layer the second pattern comprising a plurality of spaced voids registered with separate ones of the zones of the first pattern; ion implanting impurities of the second conductivity type into the areas beneath the voids of the second pattern; heating in an oxidizing atmosphere sufficient to cause the impurities of the second pattern to penetrate essentially completely through the epitaxial layer and sufficient simultaneously to form oxide regions on the surface of the epitaxial layer selectively in the voids in the masking layer; and removing the masking layer by etching in a solution which substantially affects neither the selectively formed oxide nor the semiconductor material.

Claim 14

In a method for fabricating a semiconductor integrated circuit device including a transistor comprising the steps of forming into the surface of a body of semiconductive material of a first conductivity type a first pattern comprising a plurality of zones of a second conductivity type, and forming an epitaxial layer of the first conductivity type over the surface of the body, the improvement being the steps of: forming over the epitaxial layer a masking layer of a material capable of masking oxidation and etching selectively with respect to the oxide and to the semiconductor; forming through the masking layer a second pattern comprising a plurality of spaced voids registered with separate ones of the zones of the first pattern; ion implanting impurities of the second conductivity type into the areas beneath the voids of the second pattern; heating in an oxidizing atmosphere sufficient to cause the impurities of the second pattern to penetrate essentially completely through the epitaxial layer and sufficient simultaneously to form oxide regions on the surface of the epitaxial layer selectively in the voids in the masking layer; removing the masking layer by etching in a solution which substantially affects neither the selectively formed oxide nor the semiconductor material; ion implanting buried base zones beneath and separated from the surface of the epitaxial layer; and forming emitter zones extending inward from the surface of the epitaxial layer to the base zones.

Claim 15

In a method for fabricating a semiconductor integrated circuit device including a transistor comprising the steps of forming into the surface of a body of semiconductive material of a first conductivity type a first pattern comprising a plurality of zones of a second conductivity type, and forming an epitaxial layer of the first conductivity type over the surface of the body, the improvement being the steps of: forming over the epitaxial layer a masking layer of a material capable of masking oxidation and etching selectively with respect to the oxide and to the semiconductor; forming through the masking layer a second pattern comprising a plurality of spaced voids registered with separate ones of the zones of the first pattern; ion implanting impurities of the second conductivity type into the areas beneath the voids of the second pattern; heating in an oxidizing atmosphere sufficient to cause the impurities of the second pattern to penetrate essentially completely through the epitaxial layer and sufficient simultaneously to form oxide regions on the surface of the epitaxial layer selectively in the voids in the masking layer; removing the masking layer by etching in a solution which substantially affects neither the selectively formed oxide nor the semiconductor material; ion implanting buried base zones beneath and separated from the surface of the epitaxial layer; and forming emitter zones extending inward from the surface of the epitaxial layer to the base zones.

Claim 16

A method as recited in claim 12 wherein the buried base zones and emitter zones are formed by: depositing an oxide layer containing impurities of the first conductivity type; forming a plurality of spaced voids to provide exposed regions of epitaxial layer above separate ones of the zones of the first pattern and exposed regions of epitaxial layer above separate ones of the zones of the second pattern thereby producing a mask; heating the oxide layer sufficient that oxide layer impurities of the first conductivity type diffuse into those portions of the epitaxial layer essentially only underneath the remainder of the oxide layer And form a distribution of first conductivity type impurities whose concentration decreases with increasing distance into the epitaxial layer; ion implanting impurities of the first conductivity type into the epitaxial layer through the last mentioned spaced voids to form, over the zones of the first pattern, buried base zones having a distribution of first conductivity type impurities whose concentration first increases then decreases with increasing distance into the epitaxial layer; and introducing impurities of the second conductivity type through the last-mentioned spaced voids to form distributions of second conductivity type impurities whose concentration decreases with increasing distance into the epitaxial layer thereby producing emitter zones above the base zones and producing zones with improved ohmic contact characteristics above the second pattern zones.

Claim 17

In a method for fabricating a semiconductor integrated circuit device including a transistor comprising the steps of forming into the surface of a body of semiconductive material of a first conductivity type a first pattern comprising a plurality of zones of a second conductivity type, and forming an epitaxial layer of the first conductivity type over the surface of the body, the improvement being the steps of: forming over the epitaxial layer a masking layer of a material capable of masking oxidation and etching selectively with respect to the oxide and to the semiconductor; forming through the masking layer a second pattern comprising a plurality of spaced voids registered with separate ones of the zones of the first pattern; ion implanting impurities of the second conductivity type into the areas beneath the voids of the second pattern; heating in an oxidizing atmosphere sufficient to cause the impurities of the second pattern to penetrate essentially completely through the epitaxial layer and sufficient simultaneously to form oxide regions on the surface of the epitaxial layer selectively in the voids in the masking layer; removing the masking layer by etching in a solution which substantially affects neither the selectively formed oxide nor the semiconductor material; depositing an oxide layer containing impurities of the first conductivity type; forming a plurality of spaced voids to provide exposed regions of epitaxial layer above separate ones of the zones of the first pattern and exposed regions of epitaxial layer above separate ones of the zones of the second pattern thereby producing a mask; heating the oxide layer sufficient that oxide layer impurities of the first conductivity type diffuse into those portions of the epitaxial layer essentially only underneath the remainder of the oxide layer and form a distribution of first conductivity type impurities whose concentration decreases with increasing distance into the epitaxial layer; ion implanting impurities of the first conductivity type into the epitaxial layer through the last-mentioned spaced voids to form, over the zones of the first pattern, buried base zones having a distribution of first conductivity type impurities whose concentration first increases then decreases with increasing distance into the epitaxial layer; and introducing impurities of the second conductivity type through the last-mentioned spaced voids to form distributions of second conductivity type impurities whose concentration decreases with increasing distance into the epitaxial layer thereby producing emitter zones above the base zones and producing zones with improved ohmic contact characteristics above the second pattern zone.

Claim 18

In a method for fabricating a semiconductor integrated circuit device including a transistor comprising the steps of forming into the surface of a body of semiconductive material of a first conductivity type a first pattern comprising a plurality of zones of a second conductivity type, and forming an epitaxial layer of the first conductivity type over the surface of the body, the improvement being the steps of: forming over the epitaxial layer a masking layer of a material capable of masking oxidation and etching selectively with respect to the oxide and to the semiconductor; forming through the masking layer a second pattern comprising a plurality of spaced voids registered with separate ones of the zones of the first pattern; ion implanting impurities of the second conductivity type into the areas beneath the voids of the second pattern; heating in an oxidizing atmosphere sufficient to cause the impurities of the second pattern to penetrate essentially completely through the epitaxial layer and sufficient simultaneously to form oxide regions on the surface of the epitaxial layer selectively in the voids in the masking layer; removing the masking layer by etching in a solution which substantially affects neither the selectively formed oxide nor the semiconductor material; depositing an oxide layer containing impurities of the first conductivity type; forming a plurality of spaced voids to provide exposed regions of epitaxial layer above separate ones of the zones of the first pattern and exposed regions of epitaxial layer above separate ones of the zones of the second pattern thereby producing a mask; heating the oxide layer sufficient that oxide layer impurities of the first conductivity type diffuse into those portions of the epitaxial layer essentially only underneath the remainder of the oxide layer and form a distribution of first conductivity type impurities whose concentration decreases with increasing distance into the epitaxial layer; ion implanting impurities of the first conductivity type into the epitaxial layer through the last-mentioned spaced voids to form, over the zones of the first pattern, buried base zones having a distribution of first conductivity type impurities whose concentration first increases then decreases with increasing distance into the epitaxial layer; and introducing impurities of the second conductivity type through the last-mentioned spaced voids to form distributions of second conductivity type impurities whose concentration decreases with increasing distance into the epitaxial layer thereby producing emitter zones above the base zones and producing zones with improved ohmic contact characteristics above the second pattern zone.