Patent ID: 7226835

Claim:
A method for forming emitter contact structures for a bipolar transistor technology, comprising: providing a collector region; providing a base region adjacent the collector region; providing an emitter region comprising a total emitter area (A E ), an emitter contact region (A C ) and an emitter non-contact region (A NC ); providing a required range for a current gain (H fe ) of said bipolar transistor wherein said current gain is the ratio of a collector current of said bipolar transistor to a base current of said bipolar transistor; determining a first current ratio of said bipolar transistor wherein said first current ratio is given by the ratio of a base current density in said emitter contact region of said bipolar transistor to a collector current density of said bipolar transistor (J BC /J C ); determining a second current ratio of said bipolar transistor wherein said second current ratio is given by the ratio of a base current density in said emitter non-contact region of said bipolar transistor to the collector current density of said bipolar transistor (J BNC /J C ); determining a range for an emitter area ratio of the total emitter area to the emitter non-contact region from said first current ratio and said second current ratio; determining a required range of emitter contact area A C from said range of said emitter area ratio; and forming said emitter contact structure within said required range.