Bipolar transistor structure on semiconductor fin and methods to form same

A bipolar transistor structure comprising:

• a semiconductor fin on a substrate, the semiconductor fin having a first doping type, a length in a first direction, and a width in a second direction perpendicular to the first direction, wherein the semiconductor fin includes:
• a first portion, and
• a second portion coupled to a base contact and adjacent the first portion along the length of the semiconductor fin, wherein a dopant concentration of the second portion is greater than a dopant concentration of the first portion;
• a first emitter/collector (E/C) material between and contacting a first sidewall of a first spacer horizontally adjacent the first E/C material and a first sidewall of the second portion, the first E/C material being along the width of the semiconductor fin, and the first E/C material having a second doping type opposite the first doping type and having a first width;
• and
• a second E/C material between and contacting a first sidewall of a second spacer horizontally adjacent the second E/C material and a second sidewall of the second portion, the second E/C material being along the width of the semiconductor fin, and the second E/C material having the second doping type and having a second width different from the first width of the first E/C material;
• an insulator layer separating the first and second E/C materials from the substrate, wherein the insulator layer contacts a portion of the first and second sidewalls of the semiconductor fin, a second sidewall of the first spacer, and a second sidewall of the second spacer,
• wherein a horizontal distance between the first sidewall of the semiconductor fin and the first spacer is different than a horizontal distance between the second sidewall of the semiconductor fin and the second spacer, and wherein a top surface of the first spacer and a top surface of the second spacer extend above a top surface of the semiconductor fin.

A method of forming a bipolar transistor structure, the method comprising:

• forming a semiconductor fin on a substrate, the semiconductor fin having a first doping type, a length in a first direction, and a width in a second direction perpendicular to the first direction;
• forming an insulator layer on the substrate;
• forming a first emitter/collector (E/C) material adjacent a first sidewall of the semiconductor fin along the width of the semiconductor fin, the first E/C material having a second doping type opposite the first doping type;
• forming a second E/C material adjacent a second sidewall of the semiconductor fin along the width of the semiconductor fin, the second E/C material having the second doping type,
• wherein a width of the first E/C material is different from a width of the second E/C material;
• forming a first spacer over the substrate and horizontally distal to the first sidewall of the semiconductor fin, wherein a first sidewall of the first spacer contacts the first E/C material;
• and
• forming a second spacer over the substrate and horizontally distal to the second sidewall of the semiconductor fin, wherein a first sidewall of the second spacer contacts the second E/C material, and wherein a top surface of the first spacer and a top surface of the second spacer extend above a top surface of the semiconductor fin,
• wherein the insulator layer separates the first and second E/C materials from the substrate, wherein the insulator layer contacts a portion of the first and second sidewalls of the semiconductor fin, a second sidewall of the first spacer, and a second sidewall of the second spacer, and
• wherein a first horizontal distance between the first sidewall of the semiconductor fin and the first spacer is different than a second horizontal distance between the second sidewall of the semiconductor fin and the second spacer, the first horizontal distance defines a first width of the first E/C material, and the second horizontal distance defines a second width of the second E/C material different from the first width of the first E/C material, and
• wherein the first E/C material contacts and extends between the first sidewall of the semiconductor fin and the first spacer, and wherein the second E/C material contacts and extends between the second sidewall of the semiconductor fin and the second spacer.