Silicon carbide power devices having trench-based silicon carbide charge coupling regions therein

• US 6,313,482 B1
• Filed: 05/17/1999
• Issued: 11/06/2001
• Est. Priority Date: 05/17/1999
• Status: Expired due to Term

• Current Assignee: Hanger Solutions, LLC (IP Investments Group LLC)
• Original Assignee: North Carolina State University (University of North Carolina System)
• Inventors: Baliga, Bantval Jayant
• Primary Examiner(s): Chaudhuri, Olik
• Assistant Examiner(s): Wille, Douglas A.
• Application Number:
  US09/312,980
• Time in Patent Office: 904 Days
• Field of Search: 257/77, 257/168, 257/266, 257/267, 257/280, 257/339, 257/409, 257/471, 257/472, 257/487, 257/492, 257/493, 257/653, 257/654
• US Class Current: 257/77
• 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 29/0634 Multiple reduced surface field (multi-RESURF) structures, e.g. double RESURF, charge compensation, cool, superjunction (SJ), 3D-RESURF, composite buffer (CB) structures
• CPC Class Codes: H01L 29/0649 Dielectric regions, e.g. SiO2 regions, air gaps
• CPC Class Codes: H01L 29/1608 Silicon carbide
• 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 29/8083 Vertical transistors SIT H01L29/7722
• CPC Class Codes: H01L 29/872 Schottky diodes

Abstract

Silicon carbide power devices having trench-based charge coupling regions include a silicon carbide substrate having a silicon carbide drift region of first conductivity type (e.g., N-type) and a trench therein at a first face thereof. A uniformly doped silicon carbide charge coupling region of second conductivity type (e.g., an in-situ doped epitaxial P-type region) is also provided in the trench. This charge coupling region forms a P-N rectifying junction with the drift region that extends along a sidewall of the trench. The drift region and charge coupling region are both uniformly doped at equivalent and relatively high net majority carrier doping concentrations (e.g., 1×10¹⁷ cm⁻³) so that both the drift region and charge coupling region can be depleted substantially uniformly when blocking reverse voltages. This combination of preferred drift and charge coupling regions improves the electric field profile in the drift region to such an extent that very low forward on-state drift region resistance can be achieved simultaneously with very high reverse blocking voltage capability. Silicon carbide switching devices that can advantageously use the preferred combination of drift and charge coupling regions include Schottky barrier rectifiers (SBRs), junction field effect transistors (JFETs) and metal-oxide-semiconductor field effect transistors (MOSFETs).

Claims

1. A silicon carbide Schottky rectifier, comprising:

a silicon carbide substrate having a uniformly doped silicon carbide drift region of first conductivity type therein;

first and second trenches having widths W_T1, and W_T2, respectively, in said uniformly doped silicon carbide drift region, said first and second trenches defining a silicon carbide drift region mesa therebetween having a width W_M and a first conductivity type doping concentration N_DM therein;

first and second uniformly doped silicon carbide charge coupling regions of second conductivity type in said first and second trenches, respectively, said first uniformly doped silicon carbide charge coupling region forming a first P-N rectifying junction with said silicon carbide drift region mesa along a sidewall of said first trench and said second uniformly doped silicon carbide charge coupling region forming a second P-N rectifying function with said silicon carbide drift region mesa along a sidewall of said second trench; and

a Schottky rectifying contact on said silicon carbide drift region mesa;

wherein the second conductivity type doping concentrations in said first and second silicon carbide charge coupling regions equal N_CC1 and N_CC2, respectively;

wherein 0.5×

10¹³ cm<sup>−

2</sup>≦

(N_DM)(W_M)≦

5.0×

10¹³ cm<sup>−

2</sup>; and

wherein (N_DM)(W_M)=½

(N_CC1)(W_T1)+½

(N_CC2)(W_T2).

2. The Schottky rectifier of claim 1, further comprising a first silicon carbide contact region of first conductivity type on said silicon carbide drift region mesa and forming a nonrectifying junction therewith, said first silicon carbide contact region having a net majority carrier doping concentration therein of less than 5×

10¹⁶ cm<sup>−

3</sup>; and

wherein said Schottky rectifying contact forms a Schottky rectifying junction with said first silicon carbide contact region.

3. The Schottky rectifier of claim 2, further comprising a second silicon carbide contact region of second conductivity type in said first trench, said second silicon carbide contact region having a net majority carrier doping concentration therein of greater than 5×

10¹⁷ cm<sup>−

3</sup> and forming a nonrectifying junction with said first uniformly doped silicon carbide charge coupling region.

4. A silicon carbide power device, comprising:

a silicon carbide substrate having a uniformly doped silicon carbide drift region of first conductivity type therein;

first and second trenches having widths W_T1, and W_T2, respectively, in said uniformly doped silicon carbide drift region, said first and second trenches defining a silicon carbide drift region mesa therebetween having a width W_M and a first conductivity type doping concentration N_DM therein;

first and second uniformly doped silicon carbide charge coupling regions of second conductivity type in said first and second trenches, respectively, said first uniformly doped silicon carbide charge coupling region forming a first P-N rectifying junction with said silicon carbide drift region mesa along a sidewall of said first trench and said second uniformly doped silicon carbide charge coupling region forming a second P-N rectifying junction with said silicon carbide drift region mesa along a sidewall of said second trench;

wherein the second conductivity type doping concentrations in said first and second silicon carbide charge coupling regions equal N_CC1 and N_CC2;

respectively;

wherein 0.5×

10¹³ cm<sup>−

2</sup>≦

(N_DM)(W_M)≦

5.0×

10¹³ cm<sup>−

2</sup>; and

wherein (N_DM)(W_M)=½

(N_CC1)(W_T1)+½

(N_CC2)(W_T2).

5. The power device of claim 4, further comprising:

a Schottky rectifying contact electrically coupled to said silicon carbide drift region mesa.

6. The power device of claim 5, further comprising a first silicon carbide contact region of first conductivity type on said silicon carbide drift region mesa and forming a nonrectifying junction therewith, said first silicon carbide contact region having a net majority carrier doping concentration therein of less than 5×

10¹⁶ cm<sup>−

3</sup>; and

wherein said Schottky rectifying contact forms a Schottky rectifying junction with said first silicon carbide contact region.

7. The power device of claim 6, further comprising a second silicon carbide contact region of second conductivity type in said first trench, said second silicon carbide contact region having a net majority carrier doping concentration therein of greater than 5×

10¹⁷ cm<sup>−

3</sup> and forming a nonrectifying junction with said first uniformly doped silicon carbide charge coupling region.

8. The power device of claim 4, further comprising an insulated gate electrode in said first trench;

and wherein said first silicon carbide charge coupling region extends between said insulated gate electrode and a bottom of said first trench.

10. The power device of claim 5, further comprising:

a silicon carbide source region of first conductivity type on said silicon carbide drift region mesa, said silicon carbide source region disposed between said silicon carbide drift region and a first face of said silicon carbide substrate and having a majority carrier doping concentration therein of greater than 5×

10¹⁷ cm<sup>−

3</sup> cm<sup>−

3</sup> and greater than N_DM; and

a silicon carbide gate region of second conductivity type in said first trench, said silicon carbide gate region disposed between said silicon carbide charge coupling region and the first face and having a majority carrier doping concentration therein of greater than 5×

10¹⁷ cm<sup>−

3</sup> and greater than N_CC1.

11. The power device of claim 10, further comprising a silicon carbide channel region of first conductivity type extending between said silicon carbide source region and said silicon carbide drift region, said silicon carbide channel region having a majority carrier doping concentration therein of less than 5×

10¹⁶ cm<sup>−

3</sup> and less than N_DM.

9. A silicon carbide power device, comprising:

a silicon carbide substrate having a uniformly doped silicon carbide drift region of first conductivity type therein;

first and second trenches having widths W_T1 and W_T2, respectively, in said uniformly doped silicon carbide drift region, said first and second trenches defining a silicon carbide drift region mesa therebetween having a width W_M and a first conductivity type doping concentration N_DM therein;

an insulated gate electrode in said first trench;

first and second uniformly doped silicon carbide charge coupling regions of second conductivity type in said first and second trenches, respectively, said first uniformly doped silicon carbide charge coupling region forming a first P-N rectifying junction with said silicon carbide drift region mesa along a sidewall of said first trench and said second uniformly doped silicon carbide charge coupling region forming a second P-N rectifying function with said silicon carbide drift region mesa along a sidewall of said second trench; and

a silicon carbide base region of second conductivity type on said silicon carbide drift region mesa, said silicon carbide base region extending to the sidewall of said first trench and forming a rectifying junction with said silicon carbide drift region at a location opposite said insulated gate electrode;

wherein said first silicon carbide charge coupling region extends between said insulated gate electrode and a bottom of said first trench;

wherein the second conductivity type doping concentrations in said first and second silicon carbide charge coupling regions equal N_CC1 and N_CC2, respectively;

wherein 0.5×

10¹³ cm<sup>−

2</sup>≦

(N_DM)(W_M)≦

5.0×

10¹³ cm<sup>−

2</sup>; and

wherein (N_DM)(W_M)=½

(N_CC1)(W_T1)+½

(N_CC2)(W_T2).

12. A silicon carbide power device, comprising:

a silicon carbide substrate having a uniformly doped silicon carbide drift region of first conductivity type therein;

first and second trenches having widths W_T1, and W_T2, respectively, in said uniformly doped silicon carbide drift region, said first and second trenches defining a silicon carbide drift region mesa therebetween having a width W_M and a first conductivity type doping concentration N_DM therein;

a first insulated gate electrode in said first trench;

a second gate electrode in said second trench;

a first uniformly doped silicon carbide charge coupling region of second conductivity type extending between said first insulated gate electrode and a bottom of said first trench and forming a first P-N rectifying junction with said silicon carbide drift region mesa along a sidewall of said first trench;

a second uniformly doped silicon carbide charge coupling region of second conductivity type extending in said second trench and forming a second P-N rectifying junction with said silicon carbide drift region mesa along a sidewall of said second trench, said first and second uniformly doped silicon carbide charge coupling regions having sufficient second conductivity type charge therein to provide matched charge coupling across said silicon carbide drift region mesa; and

a silicon carbide base region of second conductivity type on said silicon carbide drift region mesa, said silicon carbide base region extending to the sidewall of said first trench and forming a rectifying junction with said silicon carbide drift region mesa.

13. The power device of claim 12, wherein 0.5×

10¹³ cm<sup>−

2</sup>≦

(N_DM)(W_M)≦

5.0×

10¹³ cm<sup>−

2</sup>.

14. The power device of claim 12, wherein the second conductivity type doping concentrations in said first and second silicon carbide charge coupling regions equal N_CC1, and N_CC2, respectively;

and wherein ½

(N_CC1)(W_T1)+½

(N_CC2)(W_T2)≦

5.0×

10¹³ cm<sup>−

2</sup>.

15. The power device of claim 13, wherein the second conductivity type doping concentrations in said first and second silicon carbide charge coupling regions equal N_CC1, and N_CC2, respectively;

and wherein ½

(N_CC1)(W_T1)+½

(N_CC2)(W_T2)≦

5.0×

10¹³ cm<sup>−

2</sup>.

16. The power device of claim 15, wherein (N_DM)(W_M)=½

(N_CC1)(W_T1)+½

(N_CC2)(W_T2).

17. A silicon carbide power device, comprising:

a silicon carbide substrate having a uniformly doped silicon carbide drift region of first conductivity type therein;

first and second trenches having widths W_T1 and W_T2, respectively, in said uniformly doped silicon carbide drift region, said first and second trenches defining a silicon carbide drift region mesa therebetween having a height, a width W_M and a first conductivity type doping concentration N_DM therein; and

first and second uniformly doped silicon carbide charge coupling regions of second conductivity type within said first and second trenches, respectively, said first uniformly doped silicon carbide charge coupling region forming a first P-N rectifying junction with said silicon carbide drift region mesa along a sidewall and bottom of said first trench and said second uniformly doped silicon carbide charge coupling region forming a second P-N rectifying junction with said silicon carbide drift region mesa along a sidewall and bottom of said second trench, and wherein said first and second uniformly doped silicon carbide charge coupling regions are of sufficient thickness within said first and second trenches, respectively, to provide charge coupling over at least a majority of the height of said silicon carbide drift region mesa;

wherein the second conductivity type doping concentrations in said first and second silicon carbide charge coupling regions equal N_CC1 and N_CC2, respectively;

wherein 0.5×

10¹³ cm<sup>−

2</sup>≦

(N_DM)(W_M)≦

5.0×

10¹³ cm<sup>−

2</sup> ; and

wherein 0.5×

10¹³ cm<sup>−

2</sup>≦

½

(N_CC1)(W_T1)+½

(N_CC2)(W_T2)≦

5.0×

10¹³ cm<sup>−

2</sup>.