Process for making bipolar transistor with polysilicon stringer base contact

Claim 1

A process for making a base and emitter contact structure for a transistor comprising the steps of: forming an isolated island of monocrystalline silicon; forming a layer of polysilicon covered by a first layer of metal disilicide; doping the first metal disilicide layer with both P type and N type impurities where the impurities are selected such that the lower concentration impurity has a faster diffusion rate in terms of distance travelled per unit time for given diffusion conditions; forming a layer of insulating material over said metal disilicide; etching said combined three layers into the shape of an emitter contact stripe which crosses said island and which has an emitter contact pad located external to said island; forming a second layer of insulating material over the etched structure; anisotropically etching the second insulating layer until all the insulating material in planes parallel to the surface of said island is removed; forming a layer of metal disilicide over the structure; doping said second metal disilicide layer with impurities of the conductivity type which will exist in the base region of the final transistor; masking a portion of said second metal disilicide layer which is to be the base contact pad at a location outside said island; anisotropically etching away all portions of said second metal disilicide layer which lie in planes parallel to the surface of said island except that portion under said mask; and baking the resultant structure in an oven long enough and at a temperature sufficient to allow the impurities in said first metal disilicide layer to diffuse into said polysilicon and said monocrystalline silicon sufficiently to form an emitter region of the desired depth and a base region of the desired width which is in electrical contact with said stringers of said second metal disilicide layer.

Claim 11

A method of forming a contact structure having a first contact and a second contact separated by a common narrow sidewall, the method comprising: a) on a semiconductor body having a major surface, forming a first region of electrically conductive material disposed on and in contact with the semiconductor body, the first region having first sidewalls and forming the first contact; b) after forming said first region, forming a first layer, of first thickness electrically insulating material over the first region and on the first sidewalls and extending to the major surface to thereby define second sidewalls separated from the first sidewalls by the first thickness, said first layer formed by the steps of: i) depositing a layer of CVD oxide on said structure; and ii) anisotropically etching said oxide layer; and c) forming a second layer of second thickness electrically conductive material, disposed over at least the second sidewalls and extending to the major surface to thereby define third sidewalls separated from the second sidewalls by the second thickness, said second layer forming the second contact, said step of forming a second layer formed comprising the steps of: i) depositing a conductive material on said structure; and ii) anisotropically etching said conductive material to form said third sidewalls.

Claim 12

A method of forming a contact structure having a first contact and a second contact separated by a common narrow sidewall, the method comprising: a) on a semiconductor body having a major surface, forming a first region of electrically conductive material disposed on and in contact with the semiconductor body, the first region having first sidewalls and forming the first contact; b) after forming said first region, forming a first layer, of first thickness electrically insulating material over the first region and on the first sidewalls and extending to the major surface to thereby define second sidewalls separated from the first sidewalls by the first thickness, said first layer formed by the steps of: i) depositing a layer of CVD oxide on said structure; and ii) anisotropically etching said oxide layer; and c) forming a second layer of second thickness electrically conductive material, disposed over at least the second sidewalls and extending to the major surface to thereby define third sidewalls separated from the second sidewalls by the second thickness, said second layer forming the second contact, said step of forming a second layer formed comprising the steps of: i) depositing a conductive material on said structure; and ii) anisotropically etching said conductive material to form said third sidewalls.