DOUBLE DIFFUSED HIGH VOLTAGE, HIGH CURRENT NPN TRANSISTOR

• US 3,777,227 A
• Filed: 08/21/1972
• Issued: 12/04/1973
• Est. Priority Date: 08/21/1972
• Status: Expired due to Term

• Current Assignee: John R. Davis, Jr., Surinder Krishna
• Original Assignee: John R. Davis, Jr., Surinder Krishna
• Inventors: Krishna, Surinder, Davis, John R. Jr.
• Primary Examiner(s): Huckert, John W.
• Assistant Examiner(s): Wojciechowicz, E.
• Application Number:
  US05/282,624
• Time in Patent Office: 470 Days
• Field of Search: 317/235
• US Class Current: 257/578
• CPC Class Codes: H01L 21/00 Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
• CPC Class Codes: H01L 29/00 Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor H01L31/00 - H01L33/00, H10K10/00, H10N take precedence; details other than of semiconductor bodies or of electrodes thereof H01L23/00; devices consisting of a plurality of solid state components formed in or on a common substrate H01L27/00
• CPC Class Codes: H01L 29/73 Bipolar junction transistors
• CPC Class Codes: Y10S 148/04 Dopants, special
• CPC Class Codes: Y10S 148/051 Etching
• CPC Class Codes: Y10S 148/085 Isolated-integrated
• CPC Class Codes: Y10S 148/121 Plastic temperature
• CPC Class Codes: Y10S 148/135 Removal of substrate
• CPC Class Codes: Y10S 148/151 Simultaneous diffusion
• CPC Class Codes: Y10S 148/157 Special diffusion and profiles

Abstract

An NPN transistor with high voltage and high current capacities is provided in a semiconductor body having a thin internal portion and a thick integral peripheral portion. The thin portion has a substantially uniform width of greater than about 28 microns and oppositely facing surface areas each of greater than about 0.10 cm2. The thick peripheral portion has a width greater than about 150 microns and annular dimension i.e. radial width greater than 10 microns. The base region has two contiguous impurity portions. A first impurity portion adjoins a major, preferably planar surface of the semiconductor body at the peripheral portion and has an impurity concentration of boron of at least 1 X 1019 atoms per cubic centimeter at the surface and a steep impurity concentration gradient to provide good ohmic and thermal properties. A second contiguous impurity portion is in internal portions of the body between emitter and collector regions and has a lower impurity concentration of gallium and/or aluminum and shallower impurity concentration gradient than the first impurity portion. Preferably, first and second impurity portions of the base region are formed by the simultaneous diffusion of boron and gallium and/or aluminum.

Claims

1. An NPN transistor comprising:

a semiconductor body of resistivity of greater than 30 ohm-cms having first and second opposed major surfaces and thin internal and thick peripheral portions;

said thin internal portion being of substantially uniform thickness of greater than about 28 microns and having opposed surfaces each of greater than about 0.10 cm2 in area, and said thick peripheral portion being of thickness greater than about 150 microns and having an radial width greater than about 10 microns;

a base region adjoining a major surface at the peripheral portion of the body and comprising first and second impurity portions, first impurity portion adjoining said major surface and having an impurity concentration of boron of at least 1 X 1019 atoms per cubic centimeter at said major surface and steep impurity concentration gradient to provide good ohmic and thermal contact properties, and a second contiguous impurity portion in internal portions of the body between emitter and collector regions, and Having a lower impurity concentration than the first impurity portion of at least one member of the group consisting of aluminum and gallium and a shallower impurity concentration gradient than the first impurity portion; and

an emitter region of N-type impurity concentration adjoining the same major surface as the base region at at least the internal portion of the body and extending into the body to adjoin the second impurity portion of the base region and form a PN junction therewith.

2. An NPN transistor as set forth in claim 1 wherein the impurity concentration of the second impurity portion of the base region is gallium.

3. An NPN transistor as set forth in claim 1 wherein the major surface that the base and emitter regions adjoin is planar in shape.

4. An NPN transistor as set forth in claim 1 wherein the resistivity of the semiconductor body is greater than 80 ohm-cms.