Semiconductor devices having field-relief regions

• US 4,646,115 A
• Filed: 05/01/1986
• Issued: 02/24/1987
• Est. Priority Date: 12/20/1983
• Status: Expired due to Term

• Current Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: Slatter, John A. G., Shannon, John M., Coe, David J.
• Primary Examiner(s): Larkins, William D.
• Assistant Examiner(s): Mintel, William A.
• Application Number:
  US06/859,852
• Time in Patent Office: 299 Days
• Field of Search: 357/15 M, 357/15 P, 357/16, 357/22, 357/54 N, 357/54 M, 357/54 A, 357/49, 357/53, 357/90, 357/55
• US Class Current: 257/484
• 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 29/402 Field plates
• CPC Class Codes: H01L 29/407 Recessed field plates, e.g. trench field plates, buried field plates
• CPC Class Codes: H01L 29/408 with an insulating layer with a particular dielectric or electrostatic property, e.g. with static charges or for controlling trapped charges or moving ions, or with a plate acting on the insulator potential or the insulator charges, e.g. for controlling charges effect or potential distribution in the insulating layer, or with a semi-insulating layer contacting directly the semiconductor surface
• CPC Class Codes: H01L 29/7813 with trench gate electrode, e.g. UMOS transistors trench gate electrodes per se H01L29/4236
• CPC Class Codes: H01L 29/8618 Diodes with bulk potential barrier, e.g. Camel diodes, Planar Doped Barrier diodes, Graded bandgap diodes
• CPC Class Codes: H01L 29/872 Schottky diodes

Abstract

Separate areas of an active unipolar barrier, e.g. a Schottky barrier, of a semiconductor device are located between closely-spaced field-relief regions which provide the device with an improved voltage blocking characteristic. The flow of minority carriers into the adjacent body portion under forward bias is restricted by providing, at least at the areas of the field-relief regions, a layer of different material from that of the body portion and from that of the unipolar barrier-forming means. The layer of different material may form a high-impedance electrical connection with the field-relief regions, and/or it may form with the body portion a heterojunction such as, for example, a Schottky barrier of higher barrier height, a barrier between different band gap materials or a MIS structure, which heterojunction forms part of the field-relief regions.

Claims

1. A semiconductor device comprising a semiconductor body having a body portion of one conductivity type, unipolar barrier-forming means for forming an active barrier with said body portion at a plurality of separate areas, and closely-spaced surface-adjacent field-relief regions which protrude to a depth in the body below the active barrier, the separate areas of the active barrier being located between the closely-spaced field-relief regions, and the field-relief regions being sufficiently closely spaced such that depletion layers extending in the body portion from neighboring field-relief regions merge together under reverse-bias of the active barrier to provide the device with an improved voltage blocking characteristic, and said field-relief regions comprising layer means of a different material from that of the body portion and from that of the unipolar barrier-forming means provided at least in the area of the field-relief regions for enabling the field-relief regions to restrict the flow of minority carriers into the body portion under forward-bias of the active barrier, said layer means comprising a material selected from the group consisting of a dielectric material, a semi-insulating material, and a metal-based material.

2. A device as claimed in claim 1, further characterized in that a groove is provided in said surface of the body at each of said area of the field-relief regions, and said layer means of a different material is provided in the groove.

3. A device as claimed in claim 2, further characterized in that said layer means of a different material in the groove comprises the field-relief regions and forms a heterojunction with the body portion at the walls of each groove, said heterojunction restricting said flow of minority carriers under forward-bias of the active barrier.

4. A device as claimed in claim 3, further characterized in that said layer means of a different material is a metal-based layer which forms with the body portion a Schottky barrier having a higher barrier height than the active barrier.

5. A device as claimed in claim 3, further characterized in that said layer of different material is of dielectric material and is overlaid by an electrode to form the field-relief regions as a capacitive field-effect structure.

6. A device as claimed in claim 3, further characterized in that said layer of different material is of semi-insulating material.

7. A device as claimed in claim 1 or 2, further comprising an electrode layer, wherein said field-relief regions comprise regions of a second, opposite conductivity type formed in said body portion and in electrical connection with said electrode layer, and further characterized in that said layer means of a different material is located between the electrode layer and the field-relief regions to restrict current flow between the electrode layer and the field-relief regions to restrict the flow of minority carriers from these opposite conductivity type regions into the body portion under forward bias of the active barrier.

8. A device as claimed in claim 7, further characterized in that said layer means of a different material is of semi-insulating material and forms between the electrode layer and the field-relief regions a high-impedance electrical connection which restricts the current flow between the electrode layer and the field-relief regions.

9. A device as claimed in claim 7, further characterized in that said layer means of a different material is of insulating material located over a central area of each field-relief region of said opposite conductivity type so that the electrode layer contacts a peripheral portion of each field-relief region and thereby restricts the current flow between the electrode layer and the field-relief regions.

10. A device as claimed in claim 9, in which said body portion is of silicon, and further characterized in that said layer of different material is means of a silicon dioxide formed by local oxidation so as to be at least partly sunk into the field-relief regions, and in that the peripheral portion of each field-relief region, has a lower conductivity type determining doping concentration than that of said central area.

11. A device as claimed in claim 1 or 2, further characterized in that the unipolar barrier-forming means comprises a semiconductor barrier region which contains a net impurity concentration of the opposite conductivity type and which is located between said body portion and a further semiconductor region of said one conductivity type, said barrier region being at least substantially fully depleted of free charge carriers by depletion layers formed at zero bias with the body portion and further region.

12. A device as claimed in claim 1 or 2, wherein the unipolar barrier-forming means comprises a metal-based layer which is present at a surface of the body and which forms a Schottky barrier with said body portion.