Combined bipolar-field effect transistor resurf devices

• US 4,639,761 A
• Filed: 10/25/1985
• Issued: 01/27/1987
• Est. Priority Date: 12/16/1983
• Status: Expired due to Term

• Current Assignee: North American Philips Corp. (Koninklijke Philips N.V.)
• Original Assignee: North American Philips Corp. (Koninklijke Philips N.V.)
• Inventors: Jayaraman, Rajsekhar, Singer, Barry M.
• Primary Examiner(s): Larkins, William D.
• Assistant Examiner(s): Limanek, R. P.
• Application Number:
  US06/792,221
• Time in Patent Office: 459 Days
• Field of Search: 357/23.8, 357/23.4, 357/23.1, 357/13, 357/43, 357/21, 357/37, 357/89
• US Class Current: 257/336
• CPC Class Codes: H01L 21/74 Making of localized buried regions, e.g. buried collector layers, internal connections substrate contacts
• CPC Class Codes: H01L 27/0716 in combination with vertical bipolar transistors and diodes, or capacitors, or resistors
• CPC Class Codes: H01L 29/0619 with a supplementary region doped oppositely to or in rectifying contact with the semiconductor containing or contacting region, e.g. guard rings with PN or Schottky junction
• CPC Class Codes: H01L 29/0847 of field-effect transistors with insulated gate H01L29/0653 takes precedence; with a passive supplementary region between source or drain and substrate related to punch-through, capacity or isolation phenomena H01L29/1079; with LDD or DDD structure H01L29/7833; for thin film transistors H01L29/78618
• CPC Class Codes: H01L 29/0878 Impurity concentration or distribution
• CPC Class Codes: H01L 29/1083 with an inactive supplementary region, e.g. for preventing punch-through, improving capacity effect or leakage current
• CPC Class Codes: H01L 29/7816 Lateral DMOS transistors, i.e. LDMOS transistors
• CPC Class Codes: Y10S 257/901 MOSFET substrate bias

Abstract

A combined bipolar-field effect transistor RESURF device includes a lightly-doped epitaxial buried layer of a first conductivity type located between a semiconductor substrate of the first conductivity type and an epitaxial surface layer of a second conductivity type opposite to that of the first. The doping concentration and thickness of the epitaxial surface layer are selected in accordance with the Reduced Surface Field (RESURF) technique. A highly-doped buried region of the second conductivity type is located beneath the base region of the device and is sandwiched between the epitaxial buried layer and the epitaxial surface layer. The advantages of such a device include a substantially reduced "on" resistance, a more compact and flexible configuration, improved switching characteristics, reduced base device current requirements, and improved isolation. The device may be further enhanced by providing a buried annular region of the first conductivity type around and in contact with the buried region, and a surface-adjoining annular region of the first conductivity may be provided adjacent the base region.

Claims

1. A combined bipolar-field effect transistor RESURF device, which comprises;

a semiconductor substrate of a first conductivity type and having a major surface and a substrate electrode connected to the side of said substrate opposite said major surface;

a lightly-doped epitaxial buried layer of said first conductivity type on said major surface of the substrate and having a doping level at least an order of magnitude less than that of said substrate;

an epitaxial surface layer of a second conductivity type opposite to that of said first on said buried epitaxial layer, the doping concentration and thickness of said epitaxial surface layer being selected in accordance with the REduced SURface Field (RESURF) technique such that the product of doping concentration and epitaxial layer thickness (N_epi ×

d_epi) is about 10¹² atoms/cm² ;

a surface-adjoining base region of said first conductivity type in said epitaxial surface layer;

a base electrode connected to said base region;

a highly-doped buried region of said second conductivity type located beneath said base region and sandwiched between said epitaxial buried layer and said epitaxial surface layer;

a surface-adjoining source/emitter region of said second conductivity type in said base region, the source/emitter region serving both as the source and the emitter of said combined device;

a source/emitter electrode connected to said source/emitter region;

a surface-adjoining drain/collector region of said second conductivity type in said epitaxial surface layer and spaced apart from said base region, the drain/collector region serving as both the drain and the collector of said combined device;

a drain/collector electrode connected to said drain/collector region;

a surface-adjoining channel region at least partly in a peripheral portion of said base region which is nearest said drain/collector region;

an insulating layer on said surface layer and covering at least that part of said channel region which is in said base region; and

a gate electrode on said insulating layer and over at least that part of said channel region which is in said base region.

2. A combined bipolar-field effect transistor RESURF device as in claim 1, wherein said lightly-doped epitaxial buried layer is of pi conductivity type and has a doping level of about 3×

10¹⁴ atoms/cm³ and a thickness of about 30 microns, and said highly-doped buried region is of n+ conductivity type and has a doping level in the range of about 10¹⁸ -10²⁰ atoms/cm³ and a thickness in the range of about 1-2 microns.

3. A combined bipolar-field effect transistor RESURF device as in claim 1, further comprising a highly-doped buried layer of said first conductivity type in said substrate at said major surface, the doping level of said highly-doped buried layer being greater than that of said substrate.

4. A combined bipolar-field effect transistor RESURF device as in claim 3, wherein said lightly-doped epitaxial buried layer is of pi conductivity type and has a doping level of about 3×

10¹⁴ atoms/cm³ and a thickness of about 30 microns, said highly-doped buried layer is of p+ conductivity type and has a doping level of about 10¹⁸ atoms/cm³ and a thickness of about 5 microns, and said highly-doped buried region is of n+ conductivity type and has a doping level in the range of about 10¹⁸ -10²⁰ atoms/cm³ and a thickness in the range of about 1-2 microns.

5. A combined bipolar-field effect transistor RESURF device as in claim 1, 2, 3 or 4, further comprising a buried annular region of said first conductivity type around and in contact with the highly-doped buried region of said second conductivity type.

6. A combined bipolar-field effect transistor RESURF device as in claim 5, wherein said buried annular region is of p conductivity type and has a doping level in the range of about 3×

10¹⁵ -1×

10¹⁶ atoms/cm³ and a thickness in the range of about 1-2 microns.

7. A combined bipolar-field effect transistor RESURF device as in claim 5, further comprising a surface-adjoining annular region of said first conductivity type adjacent said base region.

8. A combined bipolar-field effect transistor RESURF device as in claim 7, wherein said surface-adjoining annular region is of p conductivity type and has a doping level of about 10¹⁶ atoms/cm³ and a thickness of about 1 micron.