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US 9,543,149 B2Granted
High voltage lateral extended drain MOS transistor with improved drift layer contact
AssigneeTexas Instruments Incorporated
InventorsPhilip Leland Hower, Sameer Pendharkar, Marie Denison
Life of this patent
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Abstract
An integrated circuit and method having an extended drain MOS transistor with a buried drift region, a drain end diffused link between the buried drift region and the drain contact, and a concurrently formed channel end diffused link between the buried drift region and the channel, where the channel end diffused link is formed by implanting through segmented areas to dilute the doping to less than two-thirds the doping in the drain end diffused link.
Claims20
An integrated circuit, comprising:
- a substrate, said substrate having a first conductivity type;
- a planar extended drain metal oxide semiconductor (MOS) transistor, said MOS transistor including:
- a buried drift region in said substrate so that a top surface of said buried drift region is below a top surface of said substrate, said buried drift region having an opposite conductivity type from said substrate, said buried drift region having a drain end proximate to a drain contact of said MOS transistor, and having a channel end proximate to a channel area of said MOS transistor;
- a drain end diffused link in said substrate, said drain end link diffused having said conductivity type of said buried drift region, said drain end diffused link making an electrical connection to said buried drift region at said drain end of said buried drift region and making an electrical connection to said drain contact;
- and
- a channel end diffused link in said substrate, said channel end diffused link having said conductivity type of said buried drift region, said channel end diffused link making an electrical connection to said buried drift region at said channel end of said buried drift region, said channel end diffused link being formed by ion implantation through a plurality of segmented channel end open areas so that an average doping density in said channel end diffused link is less than two-thirds an average doping density in said drain end diffused link.
3 more elements
A process of forming an integrated circuit, comprising:
- providing a substrate, said substrate having a first conductivity type;
- forming a planar extended drain MOS transistor, by a process including steps:
- forming a buried drift region in said substrate so that a top surface of said buried drift region is below a top surface of said substrate, so that said buried drift region has an opposite conductivity type from said substrate, so that said buried drift region has a drain end, and has a channel end;
- forming a link ion implant mask over a top surface of said substrate, so that said link ion implant mask has a drain end open area over said drain end of said buried drift region and has a plurality of segmented channel end open areas over said channel end of said buried drift region;
- ion implanting dopants through said drain end open area and said segmented channel end open areas concurrently into said substrate to form a drain end link implanted region under said drain end open area and to form a plurality of channel end link implanted regions under said plurality of segmented channel end open areas;
- performing an anneal operation which:
- diffuses said dopants in said drain end link implanted region to form a drain end diffused link which extends to, and makes an electrical connection with, said buried drift region;
- and
- diffuses said dopants in said channel end link implanted regions to form a channel end diffused link which extends to, and makes an electrical connection with, said buried drift region, so that an average doping density in said channel end diffused link is less than two-thirds an average doping density in said drain end diffused link;
- forming a gate dielectric layer on said substrate adjacent to said channel end diffused link opposite said buried drift region;
- forming a gate on said gate dielectric layer;
- and
- forming a drain contact on said substrate so as to make an electrical connection to said drain end diffused link.
10 more elements
Dependencies are inferred from the claim text.