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Bipolar transistor

Imported: 23 Feb '17 | Published: 22 Oct '02

Masao Kondo, Katsuya Oda, Katsuyoshi Washio

USPTO - Utility Patents

Abstract

A bipolar transistor using a B-doped Si and Ge alloy for a base in which a Ge content in an emitter-base depletion region and in a base-collector depletion region is greater than a Ge content in a base layer. Diffusion of B from the base layer can be suppressed by making the Ge content in the emitter-base depletion region and in a base-collector depletion region on both sides of the base layer greater than the Ge content in the base layer since the diffusion coefficient of B in the SiGe layer is lowered as the Ge contents increases.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing a depth profile of impurity concentrations and Ge contents of a bipolar transistor using a SiGe alloy for a base in the first embodiment according to the present invention;

FIG. 2 shows an energy band structure in an active region of an Si bipolar transistor in the first embodiment according to the present invention;

FIG. 3 shows a cross sectional structure of a bipolar transistor in the first to the seventh embodiments according to the present invention;

FIG. 4 shows a cross sectional structure for a main portion of a bipolar transistor in the first to the seventh embodiments according to the present invention;

FIG. 5 shows a cross sectional structure for a main portion of main steps in a method of manufacturing a bipolar transistor in the first to the seventh embodiments according to the present invention;

FIG. 6 shows a cross sectional structure for a main portion in main steps of a method of manufacturing a bipolar transistor in the first to the seventh embodiments according to the present invention;

FIG. 7 is a graph showing a depth profile of impurity concentrations and Ge contents of a bipolar transistor in the second embodiment according to the present invention;

FIG. 8 is a graph showing a depth profile of impurity concentration with and Ge contents of a bipolar transistor in the third embodiment according to the present invention;

FIG. 9 is a graph showing a depth profile of impurity concentrations and Ge contents of a bipolar transistor in the fourth embodiment according to the present invention;

FIG. 10 shows an energy band structure in an active region of a bipolar transistor in the fourth embodiment according to the present invention;

FIG. 11 is a graph showing a depth profile of impurity concentrations and Ge contents of a bipolar transistor in the fifth embodiment according to the present invention;

FIG. 12 is a graph showing a depth profile of impurity concentrations and Ge contents of a bipolar transistor in the sixth embodiment according to the present invention;

FIG. 13 shows an energy band structure in an active region of a bipolar transistor in the sixth embodiment according to the present invention;

FIG. 14 is a graph showing a depth profile of impurity concentrations and Ge contents of a bipolar transistor in the seventh embodiment according to the present invention;

FIG. 15 is a graph showing a relation between a Ge content and a B diffusion coefficient in an SiGe alloy layer;

FIG. 16 is a graph comparing the dependency of a highest cut-off frequency on a collector current density between the transistor in the first embodiment according to the present invention and the transistor of the prior art;

FIG. 17 is a graph showing an example of a depth profile of impurity concentrations and Ge contents in a bipolar transistor using an existent type selectively epitaxially grown SiGe base;

FIG. 18 shows an energy band structure in an active region of a bipolar transistor using an existent type selectively epitaxially grown SiGe base;

FIG. 19 shows a preamplifier for an optical transmission system in the eighth embodiment according to the present invention;

FIG. 20 is a constitutional view for a front-end module of an optical transmission system in the ninth embodiment according to the present invention;

FIG. 21 is a constitutional view of an optical transmission system in the tenth embodiment according to the present invention;

FIG. 22 shows an oscillator in a millimeter wave transmission system in the eleventh embodiment according to the present invention; and

FIG. 23 shows an oscillator in a millimeter wave transmission system in the twelfth embodiment according to the present invention.

Claims

1. A bipolar transistor using a B-doped Si and Ge alloy for a base in which the maximum value of a Ge content in an emitter-base junction depletion region and a base-collector junction depletion region is greater than an average value in a base layer, wherein said Ge content increases abruptly from a vicinity of an edge of the base layer on the emitter side to the emitter, the edge of the base layer on the emitter side being in the depth of 70-80 nm.

2. A bipolar transistor according to claim 1, wherein a grade of said Ge content in a first region in which the grade of Ge content increases from a vicinity of an edge of a base layer on a collector side to the collector is greater than the grade of said Ge content in a second region disposed in the base layer and adjacent to said first region.

3. A bipolar transistor according to claim 1, wherein the maximum of a B content of said B-doped Si and Ge alloy is 1×10

20 cm

−3.

4. A bipolar transistor using a B-doped Si and Ge alloy for a base in which for maximum value of a Ge content in an emitter-base junction depletion region and a base-collector junction depletion region is greater than an average value in a base layer,

5. A bipolar transistor according to claim 4, wherein a grade of said Ge content in a first region in which the grade of Ge content increases from a vicinity of an edge of a base layer on a collector side to the collector is greater than the grade of said Ge content in a second region disposed in the base layer and adjacent to said first region.

6. A bipolar transistor according to claim 4, wherein the maximum of a B content of said B-doped Si and Ge alloy is 1×10

20 cm

−3.

7. A bipolar transistor comprising:

8. A bipolar transistor according to claim 7, wherein said substrate is p-type Si substrate.

9. A bipolar transistor according to claim 7, wherein a grade of said Ge content in a first region in which the grade of Ge content increases from a vicinity of an edge of a base layer on a collector side to the collector is greater than the grade of said Ge content in a second region disposed in the base layer and adjacent to said first region.

10. A bipolar transistor according to claim 7, wherein the maximum of a B content of said B-doped Si and Ge alloy is 1×10

20 cm

−3.