Bipolar transistor and method of manufacturing the same
The invention relates to a semiconductor device ( 10 ) with a semiconductor body ( 12 ) comprising a bipolar transistor with an emitter region ( 1 ), a base region ( 2 ) and a collector region ( 3 ) of, respectively, a first conductivity type, a second conductivity type, opposite to the first conductivity type, and the first conductivity type, wherein, viewed in projection, the emitter region ( 1 ) is positioned above or below the base region ( 2 ), and the collector region ( 3 ) laterally borders the base region ( 2 ). According to the invention, the base region ( 2 ) comprises a highly doped subregion ( 2 A) the doping concentration of which has a delta-shaped profile in the thickness direction, and said highly doped sub-region ( 2 A) extends laterally as far as the collector region ( 3 ). Such a lateral bipolar transistor has excellent high-frequency properties and a relatively high breakdown voltage between the base and collector regions ( 2, 3 ), implying that the device is suitable for high power applications. The doping concentration lies preferably between about 10 19 and about 10 20 at/cm 3 , and the thickness of the sub-region ( 2 A) lies between 1 and 15 nm and preferably between 1 and 10 nm. The invention also comprises a method of manufacturing such a device ( 10 ).
1. A semiconductor device with a semiconductor body comprising a bipolar transistor having an emitter region, a base region and a collector region of, respectively, a first conductivity type, a second conductivity type opposite to the first conductivity type, and the first conductivity type, wherein, viewed in projection, the emitter region is surrounded by the base region, and the collector region laterally borders the base region, wherein the base region contains a highly doped sub-region, wherein a doping concentration of the highly doped sub-region has a delta-shaped profile in a thickness direction, and said highly doped sub-region extends laterally to border the collector region, wherein the collector region is not located entirely below the base region, wherein the base region further comprises a first semiconductor layer attached on the highly doped sub-region and a second semiconductor layer attached on the first semiconductor layer, and wherein the first semiconductor layer contains an SiGe mixed crystal and the second semiconductor layer contains silicon.
2. The semiconductor device as claimed in claim 1 , characterized in that the semiconductor body comprises silicon, and the doping concentration of the sub-region ranges between 10 19 and approximately 10 20 at/cm 3 , and the thickness of the sub-region ranges between 1 and 15 nm.
3. The semiconductor device as claimed in claim 1 , characterized in that the base region contains a mixed crystal of silicon and germanium.
4. The semiconductor device as claimed in claim 3 , characterized in that the sub-region is provided with first atoms that decelerate a diffusion of second atoms of the sub-region.
5. The semiconductor device as claimed in claim 4 , characterized in that the first atoms are carbon atoms.
6. The semiconductor device as claimed in claim 1 , characterized in that the first conductivity type is an n-type, and boron atoms are used for doping the base region.
7. The semiconductor device as claimed in claim 1 , characterized in that the semiconductor body comprises, below the base region, a strain-relaxed buffer (SRB) layer.
8. The semiconductor device as claimed in claim 1 , characterized in that the semiconductor body is separated from a semiconductor substrate by an electrically insulating layer.
9. The semiconductor device as claimed in claim 1 , characterized in that a first injection current of electrons flows from the emitter region to the base region, a second injection current of electrons flows from the emitter region to the collector region, the first injection current of electrons always being larger than the second injection current of electrons.
10. The semiconductor device as claimed in claim 1 , characterized in that the device is suitable for high-power application.
11. The semiconductor device as claimed in claim 1 , characterized in that the highly doped sub-region contains an SiGe mixed crystal.