Vertically stacked cascode bipolar junction transistor (BJT) pair sensor

A sensor device comprising:

• a vertically stacked cascode bipolar junction transistor pair comprising:
• a dual-base PNP bipolar junction transistor comprising a sensing base and a first sensing surface connected to the sensing base;
• a PNP bipolar junction transistor connected to the dual-base PNP bipolar junction transistor;
• and
• a resistor;
• and
• a first trench having a first sidewall, wherein a portion of the first sidewall is provided by the first sensing surface,
• wherein the PNP bipolar junction transistor and the dual-base PNP bipolar junction transistor are stacked vertically along the first trench.

A method of manufacturing a sensor device comprising a vertically stacked cascode bipolar junction transistor pair, the method comprising:

• providing a stack including a substrate, an isolation layer, an emitter layer, a first base layer, a collector-emitter layer, a second base layer, a collector layer, and a resistor layer;
• patterning the stack to form a first fin and a second fin;
• sequentially forming an oxide liner, a bottom spacer material, a first sacrificial material, a first spacer layer, a second sacrificial material, a third spacer layer, and a silicon oxide layer;
• forming a first sample trench between the first fin and the second fin;
• forming first cavities by removing the first sacrificial material and the second sacrificial material;
• forming a plurality of extrinsic bases in the first cavities, the plurality of extrinsic bases including an upper extrinsic base and a lower extrinsic base;
• forming vertical cavities in the plurality of extrinsic bases;
• forming vertical spacers in the vertical cavities, the vertical spacers including an upper vertical spacer and a lower vertical spacer;
• forming a hanging spacer, which protects the upper extrinsic base and the upper vertical spacer;
• and
• replacing the lower vertical spacer with a metal sensing surface, wherein a portion of a sidewall of the first sample trench is provided by the metal sensing surface,
• wherein the first sample trench extends through the sensor device.