TRENCH MOSFET HAVING A TOP SIDE DRAIN
First Claim
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1. A trench MOSFET having a top side drain comprising:
- a substrate of a first conductivity type;
an epitaxial layer of the first conductivity type onto said substrate, wherein said epitaxial layer has a lower doping concentration than said substrate;
an active area comprising a plurality of gate trenches filled with gate material, surrounded by a body region of a second conductivity type, and flanked by a source region of the first conductivity type;
a top side drain formed in a wide trench in a termination area and comprising a top drain metal connected to said epitaxial layer through a plurality of trenched drain contacts each filled with a contact metal plug, wherein said wide trench is formed simultaneously when said gate trenches are formed in said active area;
a BV sustaining area formed in the termination area and adjacent to the top side drain.
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Abstract
This invention discloses a trench MOSFET comprising a top side drain region in a wide trench in a termination area besides a BV sustaining area, wherein said top side drain comprises a top drain metal connected to an epitaxial layer and a substrate through a plurality of trenched drain contacts, wherein the wide trench is formed simultaneously when a plurality of gate trenches are formed in an active area, and the trenched drain contacts are formed simultaneously when a trenched source-body contact is formed in the active area.
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Citations
16 Claims
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1. A trench MOSFET having a top side drain comprising:
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a substrate of a first conductivity type; an epitaxial layer of the first conductivity type onto said substrate, wherein said epitaxial layer has a lower doping concentration than said substrate; an active area comprising a plurality of gate trenches filled with gate material, surrounded by a body region of a second conductivity type, and flanked by a source region of the first conductivity type; a top side drain formed in a wide trench in a termination area and comprising a top drain metal connected to said epitaxial layer through a plurality of trenched drain contacts each filled with a contact metal plug, wherein said wide trench is formed simultaneously when said gate trenches are formed in said active area; a BV sustaining area formed in the termination area and adjacent to the top side drain. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method for manufacturing a trench MOSFET having a top side drain, comprising:
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forming an epitaxial layer of a first conductivity type onto a substrate of the first conductivity type, wherein said epitaxial layer has a lower doping concentration than said substrate; applying a trench mask and etching a plurality of trenches to a determined depth in said epitaxial layer, wherein said trenches include;
a plurality of gate trenches in an active area, a gate contact trench in a gate contact area and a wide trench in a termination area;forming a gate oxide layer along inner surfaces of all said trenches and depositing gate material onto said gate oxide layer to fill into said trenches; carrying out a body dopant ion implantation over entire top surface without a body mask and performing body diffusion step to form body region of a second conductivity type; depositing a thick oxide layer onto the entire top surface to function as a contact interlayer; applying a contact mask and etching said contact interlayer to form a plurality of contact holes to expose a part top surface of said epitaxial layer; carrying out source dopant ion implantation without a source mask over the entire top surface; performing a source dopant diffusion to laterally diffuse said source dopant front a center portion between two adjacent gate trenches in said active area to adjacent channel regions; etching said epitaxial layer to further extend said contact holes in said epitaxial layer; forming a contact metal plug in each of said contact holes; depositing a front metal and applying a metal mask to pattern said front metal into a source metal, a gate metal and a top drain metal. - View Dependent Claims (16)
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Specification