POWER SEMICONDUCTOR DEVICE AND METHOD FOR MANUFACTURING THE SAME

• US 20120061749A1
• Filed: 09/12/2011
• Published: 03/15/2012
• Est. Priority Date: 09/13/2010
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: SAKAI, Takayuki
• Granted Patent: US 8,716,782 B2
• Time in Patent Office: Days
• US Class Current: 257/330
• CPC Class Codes: H01L 21/02178 the material containing aluminium, e.g. Al2O3
• CPC Class Codes: H01L 21/0228 deposition by cyclic CVD, e.g. ALD, ALE, pulsed CVD
• CPC Class Codes: H01L 21/02293 formation of epitaxial layers by a deposition process epitaxial growth per se C30B
• CPC Class Codes: H01L 21/28017 the insulator being formed after the semiconductor body, the semiconductor being silicon
• CPC Class Codes: H01L 21/28194 by deposition, e.g. evaporation, ALD, CVD, sputtering, laser deposition H01L21/28202 takes precedence
• CPC Class Codes: H01L 21/32115 Planarisation
• 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 29/66734 with a step of recessing the gate electrode, e.g. to form a trench gate electrode
• CPC Class Codes: H01L 29/7813 with trench gate electrode, e.g. UMOS transistors trench gate electrodes per se H01L29/4236

Abstract

In general, according to one embodiment, a power semiconductor device includes a first semiconductor layer of a first conductivity type, a second semiconductor layer of a second conductivity type, a trench, a gate insulating film, and a gate electrode. The second semiconductor layer is provided on the first semiconductor layer. The trench is provided from the second semiconductor layer to the first semiconductor layer. The gate insulating film is composed of an oxide film and a protective layer formed on the oxide film. The protective layer is opposed to the second semiconductor layer across the oxide film in the trench. The oxide film covers the second semiconductor layer exposed at a sidewall of the trench and includes at least one of aluminum and yttrium. The gate electrode is made of n-type polysilicon buried in the trench in direct contact with the gate insulating film.

Claims

1. A semiconductor device comprising:

a semiconductor layer of a first conductivity type;

a first semiconductor layer of the first conductivity type provided on a first surface of the semiconductor layer of the first conductivity type and having a lower first conductivity type impurity concentration than the semiconductor layer of the first conductivity type;

a second semiconductor layer of a second conductivity type provided on the first semiconductor layer;

a trench provided from the second semiconductor layer to the first semiconductor layer;

a gate insulating film composed of an oxide film and a protective layer, the oxide film covering the second semiconductor layer exposed at a sidewall of the trench and including at least one of aluminum and yttrium, and the protective layer being formed on the oxide film and opposed to the second semiconductor layer across the oxide film in the trench;

a gate electrode made of n-type polysilicon buried in the trench in direct contact with the gate insulating film and opposed to the second semiconductor layer across the gate insulating film;

an interlayer insulating film provided on the gate electrode and insulating the gate electrode from outside of the trench;

a third semiconductor layer of the first conductivity type selectively formed in a surface of the second semiconductor layer, being in contact with the gate insulating film at the sidewall of the trench, and having a higher first conductivity type impurity concentration than the first semiconductor layer;

a first electrode electrically connected to a second surface of the semiconductor layer on opposite side of the first surface; and

a second electrode electrically connected to the third semiconductor layer and the second semiconductor layer.

2. The device according to claim 1, wherein the protective layer includes one of a silicon oxide film, a silicon nitride film, and a silicon oxynitride film.

3. The device according to claim 1, wherein the protective layer is an oxygen atom layer covering a surface of the oxide film on the gate electrode side.

4. The device according to claim 1, wherein the protective layer is an nitrogen atom layer covering a surface of the oxide film on the gate electrode side.

5. The device according to claim 1, wherein the oxide film is Al₂O₃.

6. The device according to claim 1, wherein the oxide film is one of HfAl_xO_y, Y₂O₃, and HfY_xO_y.

7. The device according to claim 3, wherein the oxide film includes a single crystal with a C-axis oriented in a direction perpendicular to the surface of the second semiconductor layer exposed at the sidewall of the trench.

8. The device according to claim 4, wherein the oxide film includes a single crystal with a C-axis oriented in a direction perpendicular to the surface of the second semiconductor layer exposed at the sidewall of the trench.

9. The device according to claim 5, wherein the oxide film includes a single crystal with a C-axis oriented in a direction perpendicular to the surface of the second semiconductor layer exposed at the sidewall of the trench.

10. The device according to claim 1, further comprising:

a collector layer of the second conductivity type provided between the semiconductor layer and the first electrode.

11. A method for manufacturing a semiconductor device, comprising:

forming, on a first surface of a semiconductor layer of a first conductivity type, a first semiconductor layer of the first conductivity type having a lower first conductivity type impurity concentration than the semiconductor layer of the first conductivity type;

forming a second semiconductor layer of a second conductivity type on the first semiconductor layer;

forming a trench penetrating through the second semiconductor layer to inside of the first semiconductor layer;

forming a gate insulating film by forming an oxide film and then forming a protective layer, the oxide film covering the second semiconductor layer exposed at a sidewall of the trench and including at least one of aluminum and yttrium, and the protective layer being made of an oxygen atom layer or a nitrogen atom layer covering a surface of the oxide film;

forming a gate electrode made of n-type polysilicon buried in the trench in direct contact with the gate insulating film and opposed to the second semiconductor layer;

forming an interlayer insulating film on the gate electrode so as to insulate the gate electrode from outside of the trench;

selectively forming a third semiconductor layer of the first conductivity type in a surface of the second semiconductor layer so as to be in contact with the gate insulating film at the sidewall of the trench;

forming a first electrode so as to be electrically connected to a second surface of the semiconductor layer on opposite side of the first surface; and

forming a second electrode so as to be electrically connected to the third semiconductor layer and the second semiconductor layer.

12. The method according to claim 11, wherein in the forming a gate insulating film, the protective layer made of the oxygen atom layer covering the surface of the oxide film is formed by stopping supply of a raw material of aluminum or yttrium and supplying an oxygen raw material to the surface of the oxide film.

13. The method according to claim 11, wherein in the forming a gate insulating film, the protective layer made of the nitrogen atom layer covering the surface of the oxide film is formed by stopping supply of a raw material of aluminum or yttrium and supplying an nitrogen raw material to the surface of the oxide film.

14. The method according to claim 11, wherein the oxide film including at least one of aluminum and yttrium is Al₂O₃.

15. The method according to claim 11, wherein the oxide film including at least one of aluminum and yttrium is one of HfAl_xO_y, Y₂O₃, and HfY_xO_y.

16. The method according to claim 12, wherein the oxide film is formed by crystal growth so that a C-axis is oriented in a direction perpendicular to the surface of the second semiconductor layer exposed at the sidewall of the trench.

17. The method according to claim 13, wherein the oxide film is formed by crystal growth so that a C-axis is oriented in a direction perpendicular to the surface of the second semiconductor layer exposed at the sidewall of the trench.

18. The method according to claim 14, wherein the oxide film is formed by crystal growth so that a C-axis is oriented in a direction perpendicular to the surface of the second semiconductor layer exposed at the sidewall of the trench.

19. The method according to claim 12, wherein the oxide film is formed by ALD.

20. The method according to claim 13, wherein the oxide film is formed by ALD.