SELF-ALIGNED COMPLEMENTARY LDMOS
First Claim
1. A self-aligned LDMOS device, comprising:
- a gate having a gate oxide, and an oxide spacer on a source side of said gate;
a source region having a tap and a source spacer embedded in a source well, the tap being aligned with an edge of the oxide spacer and the source spacer being aligned with the edge of the gate polysilicon such that the source spacer is fully under the oxide spacer; and
a drain region situated opposite to the source side of said gate, the drain region having a drain embedded in a drain well.
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Abstract
The invention includes a laterally double-diffused metal-oxide semiconductor (LDMOS) having a reduced size, a high breakdown voltage, and a low on-state resistance. This is achieved by providing a thick gate oxide on the drain side of the device, which reduces electric field crowding in the off-state to reduce the breakdown voltage and forms an accumulation layer in the drift region to reduce the device resistance in the on-state. A version of the device includes a low threshold voltage version with a thin gate oxide on the source side of the device and a high threshold voltage version of the device includes a thick gate oxide on the source side. The LDMOS may be configured in an LNDMOS having an N type source or an LPDMOS having a P type source. The source of the device is fully aligned under the oxide spacer adjacent the gate to provide a large SOA, to reduce the device size and to reduce the device leakage.
23 Citations
34 Claims
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1. A self-aligned LDMOS device, comprising:
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a gate having a gate oxide, and an oxide spacer on a source side of said gate; a source region having a tap and a source spacer embedded in a source well, the tap being aligned with an edge of the oxide spacer and the source spacer being aligned with the edge of the gate polysilicon such that the source spacer is fully under the oxide spacer; and a drain region situated opposite to the source side of said gate, the drain region having a drain embedded in a drain well. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 14, 15, 16, 17, 18, 19)
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12. The self-aligned LDMOS device of claim 12, further comprising a high voltage N well extending laterally from the isolation ring to the source well on the source side of the gate.
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20. A self-aligned LDMOS device, comprising:
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a gate situated on a high voltage well, the gate having a gate oxide on the high voltage well and a polysilicon layer on the gate oxide; a source region in the high voltage well on a source side of said gate; a drain region in the high voltage well on a drain side of said gate; and wherein the gate oxide is thick on the drain side of said gate.
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21. The self-aligned LDMOS device of claim 21, the thick gate oxide having a thickness selected from the group consisting of about 400 Å
- and 600 Å
. - View Dependent Claims (22, 23, 24, 25)
- and 600 Å
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26. A method of forming a self-aligned LDMOS device, comprising the steps of:
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a) providing a high voltage well with an oxide layer and a polysilicon layer; b) etching the oxide layer and the polysilicon layer to form a source region and a drain region with a gate therebetween; c) forming a source well in the source region of the high voltage well and a drain well in the drain region of the high voltage well; d) implanting a source body in the source region extending from the source well under the gate; e) implanting a source in the source well; and f) forming an oxide spacer over the source an adjacent the gate such that the oxide spacer fully covers the source. - View Dependent Claims (27, 28, 29, 30, 31, 32, 33, 34)
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Specification