Process for forming an electrical contact through an insulation layer to a silicon semiconductor wafer thereunder

Claim 2

The process of claim 1 wherein said insulating layer comprises a layer of SiO₂.

Claim 3

The process of claim 1 or 2 wherein said contact opening in said insulating layer has an aspect ratio of at least 1, and said step of depositing said titanium layer further comprises forming a layer of titanium over said exposed silicon surface at the bottom of said contact opening ranging in thickness from about 5 to about 100 NM (50 to about 1000 Angstroms).

Claim 4

The process of one of the preceding claims including the further step of transferring said titanium coated wafer from a deposition station to an annealing station without exposing said titanium deposited thereon to any oxygen-containing gases prior to said step of annealing in the presence of a nitrogen-bearing gas.

Claim 5

The process of one of the preceding claims wherein said annealing step in said presence of said nitrogen-bearing gas further comprises initially annealing said titanium coated wafer at a temperature ranging from 500°C to 695°C to form said titanium silicide and titanium nitride.

Claim 6

The process of claim 5 wherein said annealing step in said presence of said nitrogen-bearing gas further comprises raising said annealing temperature to a range of from 800°C to 900°C after said initial annealing to convert to a more stable phase said titanium silicide initially formed within said temperature range of from 500°C to 695°C.

Claim 7

The process of claim 5 or 6 wherein said annealing step in said presence of said nitrogen-bearing gas further comprises initially annealing said titanium coated wafer at a temperature ranging from 650°C to 675°C to form said titanium silicide and titanium nitride.

Claim 8

The process of one of claims 5 to 7 wherein said annealing step in said presence of said nitrogen-bearing gas further comprises maintaining the pressure within a range of from about 1.3 * 10⁻⁴bar to about 1066 mb (100 milliTorr to about 800 Torr) during said annealing to form said titanium silicide and titanium nitride.

Claim 9

The process of one of the preceding claims wherein an optional annealing step in the presence of an oxygen-bearing gas is carried out after said step of annealing in the presence of a nitrogen-bearing gas.

Claim 10

The process of one of the preceding claims wherein said annealing step in said presence of said nitrogen-bearing gas further comprises: a) heating said titanium-coated wafer to an initial annealing temperature ranging from 500°C to 695°C at a rate of from 5°C/second to 150°C/second; b) annealing said titanium coated wafer at a temperature ranging from 500°C to 695°C for a period of from 10 to 60 seconds to form said titanium silicide and titanium nitride; and c) then raising said annealing temperature to a second annealing temperature range of from 800°C to 900°C and maintaining said wafer within said second annealing temperature range for a period of from 10 to 60 seconds to convert to a more stable phase said titanium silicide initially formed within said temperature range of from 500°C to 695°C.

Claim 11

The process of one of the preceding claims wherein said step of depositing said titanium in said contact opening on said wafer further comprises PVD sputtering said titanium.

Claim 12

The process of one of the preceding claims wherein said step of depositing said tungsten further comprises depositing said tungsten in said contact opening by a CVD process.

Claim 13

The process of one of the preceding claims wherein said step of depositing said tungsten further comprises depositing said tungsten in said contact opening by flowing a mixture of gases which include a tungsten-containing gas into a CVD station in a vacuum apparatus while maintaining a pressure ranging from 6.5 * 10⁻⁴bar to 1013 mb (500 milliTorr to 760 Torr).

Claim 14

The process of one of the preceding claims wherein said step of depositing said tungsten in said contact opening further comprises flowing a gaseous mixture comprising WF₆ and H₂ gases and an inert carrier gas through the deposition station.

Claim 15

The process of claim 14 wherein said step of flowing WF₆ and H₂ gases and an inert carrier gas through the deposition station is effected at a rate of from 20 to 200 sccm of WF₆; from 100 to 5000 sccm of said inert carrier gas; and from 300 to 3000 sccm of hydrogen.

Claim 16

The process of one of the preceding claims wherein said step of depositing said tungsten in said contact opening further comprises mounting said wafer on a susceptor in a CVD station and maintaining the temperature of said susceptor within a range of from 350°C to 525°C during said deposition.

Claim 17

The process of one of the preceding claims wherein said station for deposition of said titanium over said surfaces of said insulating layer and on said exposed portion of said silicon wafer; and/or said annealing station for annealing said titanium to form said titanium silicide and titanium nitride; and/or said station for depositing a layer of tungsten over insulating layer to fill said contact opening with tungsten are all located in separate chambers of the same vacuum apparatus whereby said wafer may be transported from one chamber to another without exposing said wafer to contamination.

Claim 18

A process for forming low resistance, low defect density, planar electrical contacts through a SiO₂ insulation layer to a silicon semiconductor wafer thereunder which comprises: a) sputtering depositing, in a PVD station in a vacuum apparatus, a layer of titanium over: i) exposed surfaces of said insulation layer, including sidewall insulation surfaces of a contact opening previously formed through said insulation layer to said silicon wafer; and ii) a surface of said silicon wafer exposed by said contact opening; b) transferring said titanium-coated wafer from said PVD station to an annealing station in a vacuum apparatus without exposing said titanium to oxygen-containing gases; c) initially annealing said deposited titanium at said annealing station within a temperature range of from 500°C to 695°C in the presence of a nitrogen-bearing gas, and in the absence of an oxygen-containing gas, to form titanium silicide over the exposed silicon wafer surface at the bottom of said contact opening and titanium nitride over said insulation surface and said titanium silicide; d) further annealing said titanium nitride and said titanium silicide within a temperature range of from 800°C to 900°C; e) transferring said wafer from said annealing station to a CVD station in a vacuum apparatus; f) depositing a layer of tungsten over: i) said titanium nitride surfaces on said SiO₂ insulating layer; and ii) said titanium nitride on said titanium silicide formed over said silicon substrate; to fill said contact opening with tungsten and form a planarized layer of tungsten over said titanium nitride-coated insulation layer; to thereby form a good electrical contact between said tungsten in said contact opening and said silicon wafer through said titanium nitride and titanium silicide, and a good bond between said tungsten and said titanium nitride formed on said surfaces of said insulating layer.

Claim 19

The process of claim 18 wherein said annealing step further comprises annealing said titanium coated wafer at an initial temperature ranging from 650°C to 675°C to form said titanium silicide and titanium nitride.

Claim 20

The process of claim 18 or 19 wherein said step of depositing said tungsten further comprises depositing said tungsten in said contact opening by flowing a mixture of gases which include a tungsten-containing gas into a CVD station in a vacuum apparatus while maintaining a pressure ranging from 6.5 * 10⁻⁴bar to 1013 mb (500 milliTorr to 760 Torr).

Claim 21

The process of one of claims 18 to 20 wherein said step of depositing said tungsten in said contact opening further comprises flowing a gaseous mixture comprising WF₆ and H₂ gases and an inert carrier gas through said CVD station.

Claim 22

The process of claims 18 to 21 wherein said step of depositing said tungsten in said contact opening further comprises flowing nitrogen through said CVD with said mixture of WF₆ and H₂ gases and an inert carrier gas.

Claim 23

The process of one of claims 18 to 22 wherein said step of depositing said tungsten in said contact opening further comprises mounting said wafer on a susceptor in said CVD station and maintaining the temperature of said susceptor within a range of from 350°C to 525°C during said tungsten deposition.

Claim 24

The process of one of claims 18 to 23 wherein said PVD titanium sputtering step, said annealing step, and said tungsten CVD step are all carried out in the same chamber in said vacuum apparatus.

Claim 25

A process for forming low resistance, low defect density, electrical contacts through a SiO₂ insulation layer to a silicon semiconductor wafer thereunder which comprises: a) sputter depositing, in a PVD station in a vacuum apparatus, a layer of titanium over: i) exposed surfaces of said insulation layer, including sidewall insulation surfaces of a contact opening previously formed through said insulation layer to said silicon wafer; and ii) a surface of said silicon wafer exposed by said contact opening to a thickness of from 5 to 100 NM (50 to 1000 Angstroms) over said silicon surface; b) transferring said titanium-coated wafer from said PVD station to an annealing station in a vacuum apparatus without exposing said titanium to oxygen-containing gases; c) initially annealing said deposited titanium at said annealing station within a temperature range of from 500°C to 695°C in the presence of a nitrogen-bearing gas, and in the absence of an oxygen-containing gas, to form titanium silicide over the exposed silicon wafer surface at the bottom of said contact opening and titanium nitride over said insulation surface and said titanium silicide; d) further annealing said titanium nitride and said titanium silicide within a temperature range of from 800°C to 900°C; e) transferring said wafer from said annealing station to a CVD station in a vacuum apparatus; f) depositing a layer of tungsten over said titanium nitride surfaces on said SiO₂ insulating layer and said titanium silicide surface over said silicon substrate to fill said contact opening with tungsten by a CVD process which comprises: i) mounting said wafer on a susceptor in said CVD station; ii) flowing a mixture of WF₆ and H₂ gases and an inert carrier gas through the deposition station at a rate of from 20 to 200 sccm of WF₆, from 100 to 5000 sccm of said inert carrier gas, and from 300 to 3000 sccm of hydrogen; iii) maintaining the temperature of said susceptor within a range of from 350°C to about 525°C during said CVD deposition; and iv) maintaining a pressure in said CVD station ranging from 6.5 * 10⁻⁴bar to 1013 mb (500 milliTorr to 760 Torr) during said CVD deposition; to thereby form a good electrical contact between said tungsten in said contact opening and said silicon wafer through said titanium nitride and titanium silicide, and a good bond between said tungsten and said titanium nitride formed on said surfaces of said insulating layer.