Heterobipolar transistor and method of fabricating the same
AssigneeFujitsu Limited
InventorsHidekazu Sato, Takae Sukegawa, Kousuke Suzuki
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Abstract
The present invention realizes a heterobipolar transistor using a SiGeC base layer in order to improve its electric characteristics. Specifically, the distribution of carbon and boron within the base layer is controlled so that the concentration of boron is higher than the concentration of carbon on the side bordering on the emitter layer, and upon the formation of the emitter layer, both boron and carbon are dispersed into a portion of the emitter layer that comes into contact with the base layer.
Claims24
A heterobipolar transistor comprising:
- an n-type silicon collector layer;
- a base layer formed on said n-type silicon collector layer and made of a p-type SiGeC mixed crystal layer doped with boron;
- and
- an n-type silicon emitter layer formed on the base layer and containing boron at a concentration exceeding 7×1017 cm−3;
- wherein at least a portion of said base layer including a boundary with said emitter layer has a higher concentration of boron than a concentration of carbon.
A heterobipolar transistor fabrication method comprising steps of:
- forming an n-type collector layer by forming a first n-type silicon layer on a substrate;
- forming a p-type base layer by depositing a SiGeC mixed crystal layer containing boron on said n-type collector layer so that the concentration of carbon exceeds the concentration of boron, and then continuing to deposit said SiGeC mixed crystal layer so that the concentration of boron exceeds the concentration of carbon;
- and
- forming an emitter layer by depositing a second n-type silicon layer on said p-type base layer.
Dependencies are inferred from the claim text.