Stacked LDD high frequency LDMOSFET
AssigneeInstitute of Microelectronics
InventorsJun Cai, Pang Dow Foo, Narayanan Balasubramanian
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Abstract
A novel silicon RF LDMOSFET structure based on the use of a stacked LDD, is disclosed. The LDD has been modified from a single layer of N type material to a stack of three layers. These are upper and lower N type layers with a P type layer between them. The upper N type layer is heavily doped to reduce the on-resistance of the device, while the lower N type layer is lightly doped to reduce the output capacitance, thereby improving the high frequency performance. The middle P layer is heavily doped which allows it to bring about pinch-off of the two N layers, thereby raising the device's breakdown voltage. A process for manufacturing the device, as well as experimental data concerning its performance are also given.
Claims13
A multi-layer lateral double diffused structure, comprising:
- a topmost layer of N type silicon;
- a middle layer of P type silicon;
- and
- a bottommost layer of N type silicon, having a thickness between about 1,000 and 6,000 Angstroms, said structure being part of a power MOSFET that has a gate and a drain;
- and said structure being located between said gate and said drain.
A stacked high frequency LDMOSFET, comprising:
- a P+ silicon substrate on which has been deposited an epitaxial layer of P-silicon having an upper surface;
- a P+ sinker region that extends downwards from said upper surface through the P− epitaxial layer into the P+ substrate;
- a polysilicon gate pedestal over said upper surface, there being a layer of gate oxide between the pedestal and the upper surface;
- an N+ source region on a first side of said gate pedestal and a P− body under the gate extending into said source region;
- a drain region on an opposing second side of the gate there being a separation region between the gate and the drain region;
- in said separation region, a first N type LDD layer that extends downward from said upper surface to a first interface;
- in said separation region, a P type LDD layer that extends downward from said first interface to a second interface;
- and
- in said separation region, a second N type LDD layer, having a thickness between about 1,000 and 6,000 Angstroms, that extends downward from said second interface to a third interface.
Dependencies are inferred from the claim text.