US5801075A — Method of forming trench transistor with metal sp…

Claim 1

Independent Claim 132 words

A method of forming an IGFET with a gate electrode and metal spacers in a trench, comprising the steps of: forming a trench with a bottom surface and opposing sidewalls in a substrate; forming a source and a drain in the substrate and adjacent to the bottom surface; forming metal spacers in the trench and adjacent to the sidewalls and outer portions of the bottom surface and outside a central portion of the bottom surface after forming the source and the drain; forming a gate insulator on the central portion of the bottom surface; forming protective insulators on the metal spacers; and forming a gate electrode on the gate insulator and the protective insulators such that the gate electrode is spaced from and electrically isolated from the metal spacers and the substrate.

Claim 2

Independent Claim 132 words

A method of forming an IGFET with a gate electrode and metal spacers in a trench, comprising the steps of: forming a trench with a bottom surface and opposing sidewalls in a substrate; forming a source and a drain in the substrate and adjacent to the bottom surface; forming metal spacers in the trench and adjacent to the sidewalls and outer portions of the bottom surface and outside a central portion of the bottom surface after forming the source and the drain; forming a gate insulator on the central portion of the bottom surface; forming protective insulators on the metal spacers; and forming a gate electrode on the gate insulator and the protective insulators such that the gate electrode is spaced from and electrically isolated from the metal spacers and the substrate.

Claim 3

Dependent Claim 16 words

The method of claim 1, wherein the gate insulator and the protective insulators are formed simultaneously.

Claim 4

Dependent Claim 21 words

The method of claim 1, wherein at least a portion of the gate insulator is formed before forming the metal spacers.

Claim 5

Dependent Claim 45 words

The method of claim 3, wherein forming the at least portion of the gate insulator includes forming disposable spacers in the trench, growing an oxide layer on the bottom surface between the disposable spacers, and then removing the disposable spacers before forming the metal spacers.

Claim 6

Dependent Claim 17 words

The method of claim 1, wherein forming the source and the drain includes applying a high-temperature anneal.

Claim 7

Dependent Claim 33 words

The method of claim 5, wherein forming the source and the drain includes implanting a doped layer into the substrate before forming the trench, and applying the high-temperature anneal after forming the trench.

Claim 8

Dependent Claim 26 words

The method of claim 6, wherein forming the trench includes etching completely through the doped layer, thereby splitting the doped layer into source and drain regions.

Claim 9

Dependent Claim 36 words

The method of claim 7, wherein the source and drain regions provide all doping for the source and drain, and applying the high-temperature anneal causes the source and drain regions to diffuse beneath the bottom surface.

Claim 10

Dependent Claim 95 words

The method of claim 7, wherein forming the source and the drain includes implanting a second doped layer through the bottom surface of the trench, forming disposable spacers in the trench, counterdoping a region of the second doped layer using the disposable spacers as an implant mask, thereby splitting the second doped layer into second source and drain regions, removing the disposable spacers, and applying the high-temperature anneal so that the source region and second source region merge to provide the source, and the drain region and second drain region merge to provide the drain.

Claim 11

Dependent Claim 16 words

The method of claim 5, wherein forming the trench includes etching partially through the doped layer.

Claim 12

Dependent Claim 53 words

The method of claim 10, wherein forming the source and the drain includes forming disposable spacers in the trench, counterdoping a region of the doped layer beneath the bottom surface using the disposable spacers as an implant mask, thereby splitting the doped layer into source and drain regions, and removing the disposable spacers.

Claim 13

Dependent Claim 37 words

The method of claim 1, wherein the metal spacers contact lightly doped regions of the source and the drain at the bottom surface, and contact heavily doped regions of the source and the drain at the sidewalls.

Claim 14

Dependent Claim 29 words

The method of claim 1, wherein forming the trench includes patterning a photoresist layer over the substrate, and applying an anisotropic etch through an opening in the photoresist layer.

Claim 15

Dependent Claim 46 words

The method of claim 13, wherein a length between the sidewalls corresponds to a length of the opening, and a length of a channel between the source and the drain and adjacent to the bottom surface is less than half of the length between the sidewalls.

Claim 16

Dependent Claim 24 words

The method of claim 14, wherein the length of the opening represents a minimum resolution of a lithographic system used to define the opening.

Claim 17

Dependent Claim 31 words

The method of claim 1, wherein forming the metal spacers includes depositing a blanket layer of conductive metal over the substrate and into the trench, and then applying an anisotropic etch.

Claim 18

Dependent Claim 48 words

The method of claim 1, wherein forming the metal spacers includes depositing a blanket layer of a first conductive metal over the substrate and into the trench, depositing a second blanket layer of a second conductive metal on the first conductive metal, and then applying an anisotropic etch.

Claim 19

Dependent Claim 23 words

The method of claim 1, wherein the metal spacers are selected from the group consisting of aluminum, tungsten, titanium, cobalt, and combinations thereof.

Claim 20

Dependent Claim 58 words

The method of claim 1, wherein forming the gate electrode includes depositing a blanket layer of gate electrode material over the substrate and into the trench, and then polishing the gate electrode material until the gate electrode is substantially aligned with a top surface of the substrate and no portion of the gate electrode overlaps the top surface.

Claim 21

Dependent Claim 16 words

The method of claim 1, wherein substantially all of the gate electrode is within the trench.

Claim 22

Dependent Claim 36 words

The method of claim 1, wherein the gate electrode is polysilicon, and the gate insulator and protective insulators are a continuous insulative layer selected from the group consisting of silicon dioxide, silicon nitride and silicon oxynitride.

Claim 23

Dependent Claim 12 words

The method of claim 1, wherein the IGFET is an N-channel MOSFET.

Claim 24

Dependent Claim 12 words

The method of claim 1, wherein the IGFET is a P-channel MOSFET.

Claim 25

Independent Claim 275 words

A method of forming an IGFET with a gate electrode and metal spacers in a trench, comprising the steps of: providing a semiconductor substrate; providing a photoresist layer with an opening over the substrate; applying an anisotropic etch through the opening in the photoresist layer to form a trench partially through the substrate, wherein the trench extends to a top surface of the substrate and has opposing sidewalls and a bottom surface; forming a source and a drain in the substrate, including applying a high-temperature anneal, wherein the source and the drain are adjacent to the top surface, the sidewalls, and outer portions of the bottom surface, and the source and the drain provide channel junctions for a channel adjacent to a central portion of the bottom surface; depositing a conductive metal over the substrate after forming the source and the drain, and applying an anisotropic etch to the conductive metal to form metal spacers in the trench adjacent to the sidewalls and the outer portions of the bottom surface, wherein the metal spacers contact the source and the drain at the sidewalls and the outer portions of the bottom surface; depositing a continuous insulative layer to form a gate insulator on the central portion of the bottom surface between the metal spacers and form protective insulators on sides of the metal spacers opposite the sidewalls; and depositing a gate electrode material over the substrate and then polishing the gate electrode material to form a gate electrode in the trench on the gate insulator and the protective insulators, wherein the gate electrode is spaced from and electrically isolated from the metal spacers and the substrate.

Claim 26

Independent Claim 275 words

A method of forming an IGFET with a gate electrode and metal spacers in a trench, comprising the steps of: providing a semiconductor substrate; providing a photoresist layer with an opening over the substrate; applying an anisotropic etch through the opening in the photoresist layer to form a trench partially through the substrate, wherein the trench extends to a top surface of the substrate and has opposing sidewalls and a bottom surface; forming a source and a drain in the substrate, including applying a high-temperature anneal, wherein the source and the drain are adjacent to the top surface, the sidewalls, and outer portions of the bottom surface, and the source and the drain provide channel junctions for a channel adjacent to a central portion of the bottom surface; depositing a conductive metal over the substrate after forming the source and the drain, and applying an anisotropic etch to the conductive metal to form metal spacers in the trench adjacent to the sidewalls and the outer portions of the bottom surface, wherein the metal spacers contact the source and the drain at the sidewalls and the outer portions of the bottom surface; depositing a continuous insulative layer to form a gate insulator on the central portion of the bottom surface between the metal spacers and form protective insulators on sides of the metal spacers opposite the sidewalls; and depositing a gate electrode material over the substrate and then polishing the gate electrode material to form a gate electrode in the trench on the gate insulator and the protective insulators, wherein the gate electrode is spaced from and electrically isolated from the metal spacers and the substrate.

Claim 27

Dependent Claim 84 words

The method of claim 24, wherein forming the source and the drain includes: implanting a doped layer into the substrate before forming the trench; forming the trench completely through the doped layer, thereby splitting the doped layer into source and drain regions that are adjacent to the sidewalls and spaced from the bottom surface; and applying the high-temperature anneal to activate the source and the drain regions and to diffuse the source and drain regions beneath the bottom surface to provide the channel junctions.

Claim 28

Dependent Claim 103 words

The method of claim 24, wherein forming the source and the drain includes: implanting a doped layer into the substrate before forming the trench; forming the trench partially through the doped layer such that the doped layer is adjacent to the bottom surface; forming disposable spacers in the trench; counterdoping a region of the doped layer beneath the bottom surface using the disposable spacers as an implant mask, thereby splitting the doped layer source and drain regions; removing the disposable spacers; and applying the high-temperature anneal to activate the source and drain regions, wherein the source and drain regions provide the channel junctions.

Claim 29

Dependent Claim 62 words

The method of claim 26, wherein: the doped layer includes a heavily doped upper layer adjacent to the top surface and spaced from the bottom surface, and includes a lightly doped lower layer adjacent to the bottom surface and spaced from the top surface; and the trench is formed completely through the doped upper layer and partially through the doped lower layer.

Claim 30

Dependent Claim 149 words

The method of claim 24, wherein forming the source and the drain includes: implanting a doped layer into the substrate before forming the trench; forming the trench completely through the doped layer, thereby splitting the doped layer into first source and drain regions that are adjacent to the sidewalls and spaced from the bottom surface; implanting a second doped layer through the bottom surface; forming disposable spacers in the trench; counterdoping a region of the second doped layer beneath the bottom surface using the disposable spacers as an implant mask, thereby splitting the second doped layer into second source and drain regions; removing the disposable spacers; and applying the high-temperature anneal to activate the first and second source and drain regions, to merge the first and second source regions, and to merge the first and second drain regions, wherein the second source and drain regions provide the channel junctions.

Claim 31

Dependent Claim 23 words

The method of claim 1, wherein the source and the drain contact the metal spacers at the sidewalls and at the bottom surface.

Claim 32

Dependent Claim 54 words

The method of claim 1, wherein the source and drain include lightly doped source and drain regions adjacent to the bottom surface and displaced from a top surface of the substrate, and the source and drain include heavily doped source and drain regions adjacent to the top surface and displaced from the bottom surface.

Claim 33

Dependent Claim 24 words

The method of claim 1, wherein the source and the drain form channel junctions substantially aligned with a bottom surface of the gate electrode.

Claim 34

Dependent Claim 27 words

The method of claim 1, wherein a length of a channel between the source and the drain is less than half of a length between the sidewalls.

Claim 35

Dependent Claim 27 words

The method of claim 1, wherein forming the source and the drain includes providing at least some doping for the source and drain before forming the trench.

Claim 36

Dependent Claim 34 words

The method of claim 1, wherein forming the source and the drain includes providing all doping for the source and the drain and driving-in the source and the drain before forming the metal spacers.

Claim 37

Dependent Claim 14 words

The method of claim 1, wherein the gate electrode has a planar top surface.

Claim 38

Dependent Claim 50 words

The method of claim 1, wherein forming the gate electrode includes: depositing a blanket layer of gate electrode material over the substrate and into the trench, thereby filling any remaining space in the trench; and polishing the gate electrode material to form the gate electrode with a planar top surface.

Claim 39

Dependent Claim 20 words

At The method of claim 1, wherein the metal spacers are substantially aligned with a top surface of the substrate.

Claim 40

Dependent Claim 17 words

The method of claim 1, wherein the metal spacers extend above a top surface of the substrate.

Claim 41

Dependent Claim 15 words

The method of claim 1, including forming the gate insulator after forming the metal spacers.

Claim 42

Dependent Claim 32 words

The method of claim 1, including forming the gate insulator and the protective insulators by depositing a layer of silicon dioxide at a temperature below the melting points of the metal spacers.

Claim 43

Dependent Claim 14 words

The method of claim 1, wherein the gate electrode is a non-floating gate electrode.

Claim 44

Dependent Claim 19 words

The method of claim 1, wherein the gate electrode is substantially aligned with a top surface of the substrate.

Claim 45

Dependent Claim 19 words

The method of claim 1, wherein a majority of a thickness of the gate electrode is in the trench.

Claim 46

Dependent Claim 19 words

The method of claim 1, wherein a majority of a thickness of the metal spacers is in the trench.

Claim 47

Dependent Claim 35 words

The method of claim 1, wherein a majority of a thickness of the gate electrode and the metal spacers is in the trench, and the gate electrode and the metal spacers have essentially identical thicknesses.

Claim 48

Dependent Claim 23 words

The method of claim 45, wherein essentially all of the thickness of the gate electrode and the metal spacers is in the trench.

Claim 49

Dependent Claim 14 words

The method of claim 45, wherein the gate electrode is a non-floating gate electrode.

Claim 50

Dependent Claim 14 words

The method of claim 45, wherein the gate electrode has a planar top surface.

Claim 51

Dependent Claim 22 words

The method of claim 45, wherein the source and the drain contact the metal spacers at the sidewalls and the bottom surface.

Claim 52

Dependent Claim 53 words

The method of claim 45, wherein essentially all of the thickness of the gate electrode and the metal spacers is in the trench, the gate electrode is a non-floating gate electrode with a planar top surface, and the source and the drain contact the metal spacers at the sidewalls and the bottom surface.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	2001-08-31	2002-03-02	2002-09-01	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2005-08-31	2006-03-02	2006-09-01	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2009-08-31	2010-03-02	2010-09-01	$7700.00	Window Closed / Lapsed

Method of forming trench transistor with metal spacers

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