US5340775A — Structure and fabrication of SiCr microfuses

Claim 1

Independent Claim 290 words

A method of fabricating a microfuse, deletable by low voltage electrical pulses or by laser pulses, for rerouting the various components in an integrated circuit, comprising the steps of. a) depositing a SiCr film from a target with a composition of approximately 28% Cr and 72% Si to a thickness of approximately 30 to 100 nm on a clean substrate; b) depositing a mask layer of photoresist material on the SiCr layer to define the size and shape of microfuse; c) etching away a portion of the SiCr layer exposed by the photoresist mask; d) removing the photoresist mask from the SiCr layer; e) sputter cleaning the surface of the SiCr fuse pattern by removing a portion of the upper surface of the SiCr layer; f) depositing a layer of tungsten, W, over the surface of the etched and cleaned SiCr layer, to a depth of about 50-200 nm; g) depositing a final metallization layer of an aluminum (Al) alloy over the entire exposed surface of the W layer; h) depositing a photoresist mask over the surface of the Al alloy to define the final metal pattern thereon; i) etching away the exposed areas of Al alloy down to the W layer; j) stripping the residual photoresist mask; k) etching the tungsten from the surface of the fuse to expose the SiCr fuse surface; i) annealing the structure resulting from step k) at a temperature in the range of 350°-450° C. for a period of at least 30 minutes; m) depositing a final passivation SiO 2 layer over the top surface of the structure to a thickness of about 3.0 to 4.0 μm and providing terminal contacts through the passivation layer by standard photolithographic techniques for effecting electrical contacts thereto.

Claim 2

Independent Claim 290 words

A method of fabricating a microfuse, deletable by low voltage electrical pulses or by laser pulses, for rerouting the various components in an integrated circuit, comprising the steps of. a) depositing a SiCr film from a target with a composition of approximately 28% Cr and 72% Si to a thickness of approximately 30 to 100 nm on a clean substrate; b) depositing a mask layer of photoresist material on the SiCr layer to define the size and shape of microfuse; c) etching away a portion of the SiCr layer exposed by the photoresist mask; d) removing the photoresist mask from the SiCr layer; e) sputter cleaning the surface of the SiCr fuse pattern by removing a portion of the upper surface of the SiCr layer; f) depositing a layer of tungsten, W, over the surface of the etched and cleaned SiCr layer, to a depth of about 50-200 nm; g) depositing a final metallization layer of an aluminum (Al) alloy over the entire exposed surface of the W layer; h) depositing a photoresist mask over the surface of the Al alloy to define the final metal pattern thereon; i) etching away the exposed areas of Al alloy down to the W layer; j) stripping the residual photoresist mask; k) etching the tungsten from the surface of the fuse to expose the SiCr fuse surface; i) annealing the structure resulting from step k) at a temperature in the range of 350°-450° C. for a period of at least 30 minutes; m) depositing a final passivation SiO 2 layer over the top surface of the structure to a thickness of about 3.0 to 4.0 μm and providing terminal contacts through the passivation layer by standard photolithographic techniques for effecting electrical contacts thereto.

Claim 3

Dependent Claim 23 words

The method of claim 1, wherein the depositing in step a) is to a thickness in the range of 35 to 65 nm.

Claim 4

Dependent Claim 29 words

The method of claim 1, wherein the etching in step c) is performed by a reactive ion etching (RIE) process carried out in an O 2 /CF 4 mixture.

Claim 5

Dependent Claim 39 words

The method of claim 3, wherein the etching in step k) of the tungsten layer immediately over the SiCr fuse is performed by etching in a CF 4 plasma to end-point plus a small overetch to compensate for non-uniformities.

Claim 6

Dependent Claim 67 words

The method of claim 1, wherein step a) includes the depositing of a layer of tungsten over the SiCr film to form a SiCr/W stack and wherein the mask layer of step b) is deposited over the layer of tungsten instead of over the SiCr layer and step k) is eliminated, with the etching step of step i) extending entirely through both the tungsten and SiCr layers.

Claim 7

Dependent Claim 82 words

The method of claim 5, wherein the etching in step c) is performed in two phases, the first being reactive ion etching (RIE) of the tungsten layer in CF 4 plasma and the second being RIE of the SiCr layer in an O 2 /CF 4 plasma and wherein in step e) the tungsten layer is sputter cleaned by removing at least 5.0 nm of the tungsten followed by in-situ sputtering about 50 to 200 nm of tungsten on the cleaned surface.

Claim 8

Dependent Claim 19 words

The method of claim 1 wherein the depositing in step f) is to a depth of approximately 100 nm.

Claim 9

Independent Claim 138 words

A method of fabricating a microfuse, deletable by low voltage electrical pulses or by laser pulses, for rerouting the various components in an integrated circuit, comprising the steps of: a) depositing a SiCr film form a target with a composition of approximately 28% Cr and 72% Si to a thickness of approximately 30 to 100 nm on a clean substrate; b) forming the microfuse by patterning the SiCr film; c) depositing a layer of tungsten, W, over the surface of the SiCr microfuse to a depth of about 50-200 nm; d) forming a final metallization pattern of an aluminum (Al) alloy on the exposed surface of the W layer; e) exposing the SiCr fuse surface; and f) annealing the resultant structure at a temperature in the range of 350°-450° C. for a period of at least 30 minutes.

Claim 10

Independent Claim 138 words

A method of fabricating a microfuse, deletable by low voltage electrical pulses or by laser pulses, for rerouting the various components in an integrated circuit, comprising the steps of: a) depositing a SiCr film form a target with a composition of approximately 28% Cr and 72% Si to a thickness of approximately 30 to 100 nm on a clean substrate; b) forming the microfuse by patterning the SiCr film; c) depositing a layer of tungsten, W, over the surface of the SiCr microfuse to a depth of about 50-200 nm; d) forming a final metallization pattern of an aluminum (Al) alloy on the exposed surface of the W layer; e) exposing the SiCr fuse surface; and f) annealing the resultant structure at a temperature in the range of 350°-450° C. for a period of at least 30 minutes.

Claim 11

Dependent Claim 50 words

The method of claim 8 further including the step of: g) depositing a final passivation SiO2 layer over the top surface of the structure to a thickness of about 3.0 to 4.0 μm and providing terminal contacts through the passivation layer by standard photolithographic techniques for effecting electrical contacts thereto.

Claim 12

Dependent Claim 23 words

The method of claim 8, wherein the depositing in step a) is to a thickness in the range of 35 to 65 nm.

Claim 13

Dependent Claim 33 words

The method of claim 8, wherein step e) includes etching of the tungsten layer immediately over the SiCr fuse in a CF4 plasma to end-point plus a small overetch to compensate for non-uniformities.

Claim 14

Dependent Claim 19 words

The method of claim 8, wherein the depositing in step c) is to a depth of approximately 100 nm.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1997-08-22	1998-02-21	1998-08-23	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2001-08-22	2002-02-21	2002-08-23	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2005-08-22	2006-02-21	2006-08-23	$7700.00	Window Closed / Lapsed

Structure and fabrication of SiCr microfuses

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