Method of aligning edges of emitter and its metalization in a semiconductor device

Claim 2

IN A METHOD OF MAKING A SEMICONDUCTOR DEVICE INCLUDING A BROAD AREA, MULTI-LAYER SEMICONDUCTOR WAFER COMPRISING AT LEAST A BASE LAYER HAVING FIRST AND SECOND LATERALLY ADJOINING REGIONS OF ONE CONDUCTIVITY TYPE AND A THIN EMITTER LAYER OF A DIFFERENT CONDUCTIVITY TYPE SUPERIMPOSED ON SAID FIRST REGION OF THE BASE LAER WITH WHICH IT FORMS A RECTIFYING JUNCTION, THE IMPROVEMENT COMPRISING THE STEPS OF: A. CONNECTING A METALLIC CONTACT TO THE OUTER FACE OF SAID EMITTER LAYER EXCEPT FOR A RELATIVELY SMALL AREA OF SAID FACE, ADJACENT TO AT LEAST PART OF THE BORDER BETWEEN SAID FIRST AND SECOND REGIONS OF SAID BASE LAYER, FROM WHICH SAID CONTACT IS OMITTED TO AVOID SHORT CIRCUITING SAID RECTIFYING JUNCTION IN THE VICINITY OF SAID BORDER, AND THEN B. REMOVING ENTIRELY THE PORTION OF SAID EMITTER LAYER THAT WAS DISPOSED UNDER SAID AREA.

Claim 3

The improved method of claim 1 in which said last-mentioned step is performed by treating said area of said outer face of said emitter layer with a semiconductor etchant for a sufficient length of time to remove entirely said portion of said emitter layer.

Claim 4

The improved method of claim 1 in which said lastmentioned step is performed by treating said area of said outer face of said emitter layer and an exposed surface of said second region of said base layer adjacent to said area with a semiconductor etchant for a sufficient length of time to remove entirely said portion of said emitter layer.

Claim 5

The method of claim 1 in which both base and emitter layers are diffused in said semiconductor wafer.

Claim 6

The method of claim 4 in which said first region of said base layer has a sheet resistance at said rectifying junction in the range of 300 to 3,000 ohms per square.

Claim 7

The method of claim 5 in which said emitter layer is less than 0.5 mil thick.

Claim 8

The method of claim 5 in which said emitter layer is a mesa structure and said rectifying junction is planar.

Claim 9

The method of claim 1 in which said first region of said base layer has an annular shape and circumscribes said second region, said emitter layer has an annular shape, and said area of said outer face of said emitter layer extends around the inside perimeter of said emitter layer.

Claim 10

In a method of making a semiconductor device including a broad area, multi-layer semiconductor wafer comprising at least a base layer having first and second latterly adjoining regions of one conductivity type and a thin emitter layer of a different conductivity type superimposed on said first region of the base layer with which it forms a rectifying junction, the improvement comprising the steps of: a. applying a layer of metal to the outer face of said emitter layer and to the surface of said second region of said base layer; b. removing a limited zone of said metal layer overlapping at least part of the border between said first and second regions of said base layer, thereby exposing predetermined areas of the outer face of said emitter layer and of the surface of said second region adjacent to said border; and then c. removing entirEly the portion of said emitter layer that was disposed under the predetermined exposed area of its outer face.

Claim 11

In a method of making a semiconductor device including a broad area, multi-layer semiconductor wafer comprising at least a base layer having first and second latterly adjoining regions of one conductivity type and a thin emitter layer of a different conductivity type superimposed on said first region of the base layer with which it forms a rectifying junction, the improvement comprising the steps of: a. applying a layer of metal to the outer face of said emitter layer and to the surface of said second region of said base layer; b. removing a limited zone of said metal layer overlapping at least part of the border between said first and second regions of said base layer, thereby exposing predetermined areas of the outer face of said emitter layer and of the surface of said second region adjacent to said border; and then c. removing entirEly the portion of said emitter layer that was disposed under the predetermined exposed area of its outer face.

Claim 12

The improved method of claim 9 in which said lastmentioned step is performed by treating said predetermined areas with a semiconductor etchant for a sufficient length of time to remove entirely said portion of said emitter layer.

Claim 13

The improved method of claim 9 in which said limited zone of said metal layer is removed by the steps of: a. depositing a layer of masking material on the exterior of said metal layer except for an area overlying said limited zone, and then b. treating the unmasked area of said metal layer with a metal etchant for a sufficient length of time to remove all of the metal in said limited zone.

Claim 14

The improved method of claim 11 in which the step of removing the portion of said emitter layer under said predetermined area of the outer face thereof is performed by treating said predetermined area with a semiconductor etchant for a sufficient length of time to remove entirely said portion of said emitter layer.

Claim 15

The improved method of claim 12 including the additional step of removing said layer of masking material after the step of removing the portion of said emitter layer under said predetermined area.

Claim 16

The method of claim 9 in which both base and emitter layers are diffused in said semiconductor wafer.

Claim 17

The method of claim 14 in which said first region of said base layer has a sheet resistance at said rectifying junction in the range of 300 to 3,000 ohms per square.

Claim 18

The method of claim 15 in which said emitter layer is less than 0.5 mil thick.

Claim 19

The method of claim 15 in which said emitter layer is a mesa structure and said rectifying junction is planar.

Claim 20

The method of claim 9 in which said first region of said base layer has an annular shape and circumscribes said second region, said predetermined exposed area of the surface of said second region extends along the outside perimeter of said second region, said emitter layer has an annular shape, and said predetermined exposed area of the outer face of said emitter layer extends around the inside perimeter of said emitter layer.