Double gate manufactured with locos techniques

• US 20100015770A1
• Filed: 09/18/2009
• Published: 01/21/2010
• Est. Priority Date: 05/29/2007
• Status: Abandoned Application

• Current Assignee: Alpha & Omega Semiconductor, Ltd.
• Original Assignee: Alpha & Omega Semiconductor, Inc. (Alpha & Omega Semiconductor, Ltd.)
• Inventors: Tai, Sung-Shan, Hu, Yongzhong
• Application Number:
  US12/586,257
• Publication Number:
  US 20100015770A1
• Time in Patent Office: Days
• US Class Current: 438/270
• CPC Class Codes: H01L 29/407 Recessed field plates, e.g. trench field plates, buried field plates
• CPC Class Codes: H01L 29/42368 the thickness being non-uniform
• 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

This invention discloses a method for manufacturing a trenched semiconductor power device that includes step of opening a trench in a semiconductor substrate. The method further includes a step of opening a top portion of the trench first then depositing a SiN on sidewalls of the top portion followed by etching a bottom surface of the top portion of the trench then silicon etching to open a bottom portion of the trench with a slightly smaller width than the top portion of the trench. The method further includes a step of growing a thick oxide layer along sidewalls of the bottom portion of the trench thus forming a bird-beak shaped layer at an interface point between the top portion and bottom portion of the trench.

Claims

1. A method for manufacturing a trenched semiconductor power device comprising step of opening a trench in a semiconductor substrate and said method further comprising:

opening a top portion of said trench first then depositing a SiN on sidewalls of said top portion followed by etching a bottom surface of said top portion of said trench then silicon etching to open a bottom portion of said trench with a slightly smaller width than said top portion of said trench.

2. The method of claim 1 further comprising:

growing a thick oxide layer along sidewalls of said bottom portion of said trench thus forming a bird-beak shaped layer at an interface point between said top portion and bottom portion of said trench.

3. The method of claim 2 wherein:

said step of growing said thick oxide layer along sidewalls of said bottom portion of said trench further comprising a step of growing said thick oxide layer substantially having a thickness ranging from 1000 to 3000 Angstroms.

4. The method of claim 2 wherein:

said step of growing said thick oxide layer along sidewalls of said bottom portion of said trench further comprising a step of applying LOCOS process for growing sad thick oxide layer with said bird-beak shaped layer in extending from said bottom portion to said top portion of said trench.

5. The method of claim 2 further comprising:

depositing a polysilicon into said trench followed by doping a N-type dopant followed by etching back said polysilicon to form a bottom trench-filling segment.

6. The method of claim 2 further comprising:

depositing a polysilicon into said trench followed by doping a P-type dopant followed by etching back said polysilicon to form a bottom trench-filling segment.

7. The method of claim 5 further comprising:

growing a gate oxide and an inter-segment insulation layer with a grow rate ration between a silicon and a doped polysilicon up to 1.2 to 5.

8. The method of claim 6 further comprising:

forming a top trench-filling segment by applying a second polysilicon deposition with in-situ doped polysilicon followed by a polysilicon etch-back.

9. The method of claim 7 further comprising:

forming body regions by a body implant and driving-in and forming source regions by a source implant and a source diffusion.