SEMICONDUCTOR POWER DEVICE AND METHOD FOR PRODUCING SAME

• US 20130313576A1
• Filed: 02/01/2012
• Published: 11/28/2013
• Est. Priority Date: 02/02/2011
• Status: Active Grant

• Current Assignee: ROHM Co., Ltd.
• Original Assignee: ROHM Co., Ltd.
• Inventors: Nakano, Yuki
• Granted Patent: US 9,472,405 B2
• Time in Patent Office: Days
• US Class Current: 257/77
• CPC Class Codes: H01L 21/02164 the material being a silicon oxide, e.g. SiO2
• CPC Class Codes: H01L 21/0217 the material being a silicon nitride not containing oxygen, e.g. SixNy or SixByNz H01L21/02126 and H01L21/0214 take precedence
• CPC Class Codes: H01L 21/02178 the material containing aluminium, e.g. Al2O3
• CPC Class Codes: H01L 21/02241 III-V semiconductor
• CPC Class Codes: H01L 21/02255 formation by thermal treatment H01L21/02252 takes precedence; after treatment of an insulating film H01L21/3105 and subgroups
• CPC Class Codes: H01L 21/02271 deposition by decomposition or reaction of gaseous or vapour phase compounds, i.e. chemical vapour deposition H01L21/02266 takes precedence
• CPC Class Codes: H01L 21/044 Conductor-insulator-semiconductor electrodes
• CPC Class Codes: H01L 21/049 Conductor-insulator-semiconductor electrodes, e.g. MIS contacts
• CPC Class Codes: H01L 21/28008 Making conductor-insulator-semiconductor electrodes
• CPC Class Codes: H01L 21/28264 the insulator being formed after the semiconductor body, the semiconductor being a III-V compound
• CPC Class Codes: H01L 2224/0603 Bonding areas having different sizes, e.g. different heights or widths
• CPC Class Codes: H01L 27/04 the substrate being a semiconductor body
• 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 29/0696 of cellular field-effect devices, e.g. multicellular DMOS transistors or IGBTs
• CPC Class Codes: H01L 29/1095 Body region, i.e. base region, of DMOS transistors or IGBTs cell layout H01L29/0696
• CPC Class Codes: H01L 29/1602 Diamond
• CPC Class Codes: H01L 29/1608 Silicon carbide
• CPC Class Codes: H01L 29/2003 Nitride compounds
• CPC Class Codes: H01L 29/41766 with at least part of the source or drain electrode having contact below the semiconductor surface, e.g. the source or drain electrode formed at least partially in a groove or with inclusions of conductor inside the semiconductor H01L29/41733 - H01L29/41758 take precedence
• CPC Class Codes: H01L 29/4236 within a trench, e.g. trench gate electrode, groove gate electrode
• CPC Class Codes: H01L 29/42368 : the thickness being non-uniform
• CPC Class Codes: H01L 29/513 : the variation being perpendicular to the channel plane
• CPC Class Codes: H01L 29/517 : the insulating material comprising a metallic compound, e.g. metal oxide, metal silicate H01L29/518 takes precedence
• CPC Class Codes: H01L 29/518 : the insulating material containing nitrogen, e.g. nitride, oxynitride, nitrogen-doped material
• CPC Class Codes: H01L 29/66045 : Field-effect transistors
• CPC Class Codes: H01L 29/6606 : the devices being controllable only by variation of the electric current supplied or the electric potential applied, to one or more of the electrodes carrying the current to be rectified, amplified, oscillated or switched, e.g. two-terminal devices
• CPC Class Codes: H01L 29/66068 : the devices being controllable only by the electric current supplied or the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched, e.g. three-terminal devices
• CPC Class Codes: H01L 29/66446 : with an active layer made of a group 13/15 material, e.g. group 13/15 velocity modulation transistor [VMT], group 13/15 negative resistance FET [NERFET]
• CPC Class Codes: H01L 29/7806 : the other device being a Schottky barrier diode
• CPC Class Codes: H01L 29/7811 : with an edge termination structure guard regions per se H01L29/0619; field plates per se H01L29/402
• 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 29/8611 : Planar PN junction diodes
• CPC Class Codes: H01L 29/872 : Schottky diodes

Abstract

A semiconductor power device of the present invention includes a first electrode and a second electrode, a breakdown voltage holding layer that is made of a semiconductor having a predetermined thickness and a predetermined impurity concentration, to which the first electrode and the second electrode are joined, and that has an active region in which carriers to generate electric conduction between the first electrode and the second electrode move, and an insulation film that is formed on the breakdown voltage holding layer and that has a high dielectric-constant portion having a higher dielectric constant than SiO₂ at a part contiguous to the breakdown voltage holding layer.

Claims

1. A semiconductor power device comprising:

a first electrode and a second electrode;

a breakdown voltage holding layer, the breakdown voltage holding layer being made of a semiconductor having a predetermined thickness and a predetermined impurity concentration, the first electrode and the second electrode being joined to the breakdown voltage holding layer, the breakdown voltage holding layer having an active region in which carriers to generate electric conduction between the first electrode and the second electrode move; and

an insulation film, the insulation film being formed on the breakdown voltage holding layer, the insulation film having a high dielectric-constant portion having a higher dielectric constant than SiO₂ at a part contiguous to the breakdown voltage holding layer.

2. The semiconductor power device according to claim 1, wherein the insulation film has a laminated structure including a high dielectric-constant insulation film and a low dielectric-constant insulation film, the high dielectric-constant insulation film being the high dielectric-constant portion, the low dielectric-constant insulation film being stacked on the high dielectric-constant insulation film and having a lower dielectric constant than the high dielectric-constant insulation film.

3. The semiconductor power device according to claim 1, wherein the high dielectric-constant portion is formed to be contiguous to a device-outer-peripheral part surrounding the active region.

4. The semiconductor power device according to claim 1, wherein the high dielectric-constant portion is made of SiN or Al₂O₃ or AlON.

5. The semiconductor power device according to claim 1, wherein the breakdown voltage holding layer is made of a wide bandgap semiconductor.

6. The semiconductor power device according to claim 5, wherein the wide bandgap semiconductor is SiC or GaN or diamond.

7. The semiconductor power device according to claim 1, wherein the breakdown voltage holding layer is made of a compound semiconductor.

8. The semiconductor power device according to claim 1, wherein the insulation film includes a field insulation film formed on a surface of the breakdown voltage holding layer,

the first electrode includes a Schottky electrode that penetrates the field insulation film and that makes a Schottky junction with the breakdown voltage holding layer,

the second electrode includes an ohmic electrode making an ohmic contact with the breakdown voltage holding layer, and

the field insulation film has the high dielectric-constant portion at a part contiguous to an outer peripheral area of the Schottky junction in the breakdown voltage holding layer.

9. The semiconductor power device according to claim 1, wherein, in the active region, the breakdown voltage holding layer has a field-effect transistor structure including a first conductivity type source region, a second conductivity type body region contiguous to the source region, and a first conductivity type drift region contiguous to the body region,

the first electrode includes a source electrode electrically connected to the source region,

the second electrode includes a drain electrode electrically connected to the drift region, and

the high dielectric-constant portion is formed to be contiguous to the drift region.

10. The semiconductor power device according to claim 9, wherein the field-effect transistor structure includes a vertical transistor structure in which the source region and the drift region are disposed apart from each other with the body region therebetween in a vertical direction perpendicular to the surface of the breakdown voltage holding layer,

the vertical transistor structure includes a source trench that reaches the drift region from the surface of the breakdown voltage holding layer through the source region and the body region, and

the source electrode is contiguous to the source region, the body region, and the drift region in the source trench.

11. The semiconductor power device according to claim 9, wherein the field-effect transistor structure has a trench gate structure including a gate trench formed in such a way as to straddle the source region, the body region, and the drift region,

a gate electrode facing the body region is formed in the gate trench, and

the insulation film includes a gate insulation film interposed between the gate electrode and an inner surface of the gate trench, and has the high dielectric-constant portion at a part contiguous to a bottom surface of the gate trench and/or a corner portion of the gate trench in the gate insulation film.

12. The semiconductor power device according to claim 11, wherein the gate insulation film has a laminated structure including a high dielectric-constant gate insulation film that is the high dielectric-constant portion formed at the part contiguous to the bottom surface of the gate trench and/or the corner portion of the gate trench and a low dielectric-constant gate insulation film that is stacked on the high dielectric-constant gate insulation film and that has a dielectric constant lower than the high dielectric-constant gate insulation film.

13. The semiconductor power device according to claim 11, wherein the breakdown voltage holding layer is made of SiC, and

the gate insulation film is made of Al₂O₃.

14. The semiconductor power device according to claim 11, wherein the gate insulation film includes an SiO₂ film formed at a part contiguous to the body region in a side surface of the gate trench.

15. The semiconductor power device according to claim 14, wherein the gate insulation film includes an insulation film that is stacked on the SiO₂ film and that has a dielectric constant higher than SiO₂.

16. The semiconductor power device according to claim 14, wherein the breakdown voltage holding layer is made of SiC having an Si (silicon) plane at a surface thereof, and

the gate trench is formed toward an inside of the breakdown voltage holding layer from the Si plane of the breakdown voltage holding layer made of SiC.

17. The semiconductor power device according to claim 14, wherein the high dielectric-constant portion is formed only at the bottom surface of the gate trench and/or the corner portion of the gate trench in the gate insulation film.

18. The semiconductor power device according to claim 9, wherein the field-effect transistor structure has a planar gate structure in which a gate electrode faces the body region with a gate insulation film formed on the surface of the breakdown voltage holding layer therebetween, and

the insulation film includes an interlayer insulation film formed on the breakdown voltage holding layer in such a way that the gate electrode is covered therewith, and the interlayer insulation film has the high dielectric-constant portion at a part contiguous to a transistor periphery surrounding the planar gate structure.

19. A method for producing a semiconductor power device, the semiconductor power device having a semiconductor layer made of SiC and a trench-gate type transistor structure formed in the semiconductor layer, the trench-gate type transistor structure comprising:

a first conductivity type source region;

a second conductivity type body region contiguous to the source region;

a first conductivity type drift region contiguous to the body region;

a gate trench formed in such a way as to straddle the source region, the body region, and the drift region;

a gate insulation film formed on an inner surface of the gate trench; and

a gate electrode facing the body region with the gate insulation film therebetween, the method comprising;

a step of forming the gate trench from an Si (silicon) plane of the semiconductor layer toward an inside thereof;

a step of forming a first insulation film made of SiO₂ on the inner surface of the gate trench;

a step of removing a part on a bottom surface of the gate trench in the first insulation film; and

a step of forming a second insulation film having a dielectric constant higher than SiO₂ in such a way as to cover the bottom surface of the gate trench exposed by removing the first insulation film.

20. The method for producing the semiconductor power device according to claim 19, wherein the step of forming the first insulation film is a step of forming the first insulation film according to a thermal oxidation method, and

the step of forming the second insulation film is a step of forming the second insulation film according to a CVD method.