Tungsten etch process with high selectivity to photoresist

Claim 2

A process for etching a tungsten layer on a semiconductor wafer through a patterned photoresist layer which is highly selective to photoresist and which will not laterally etch portions of the tungsten layer beneath the patterned photoresist layer which process comprises: (a) flowing SF 6 , N 2 , and Cl 2 gases into an etch chamber containing said semiconductor wafer; and (b) maintaining a plasma in said chamber during said gas flow; to thereby etch said tungsten layer while maintaining a good profile in said etched tungsten layer.

Claim 3

The process of claim 1 wherein said step of flowing said SF 6 into said etch chamber further comprises flowing said SF 6 gas into said chamber at a rate within a range of from about 10 to about 200 sccm.

Claim 4

The process of claim 2 wherein said step of flowing said N 2 into said etch chamber further comprises flowing said N 2 gas into said chamber at a rate within a range of from about 2 to about 15 volume percent of said SF 6 flow rate.

Claim 5

The process of claim 2 wherein said step of flowing said Cl 2 into said etch chamber further comprises flowing said Cl 2 gas into said chamber at a rate within a range of from about 2 to about 15 volume percent of said SF 6 flow rate.

Claim 6

The process of claim 1 wherein said step of maintaining said plasma in said etch chamber during said gas flow further comprises maintaining said plasma at a power level within a range of from about 50 to 300 watts.

Claim 7

The process of claim 1 including the further step of immersing said wafer in said etch chamber in a magnetic field during said etch process.

Claim 8

The process of claim 6 wherein said magnetic field has a magnetic moment lying in a plane parallel to the plane of said wafer in said chamber.

Claim 9

The process of claim 6 wherein the field strength of said magnetic field is at least about 100 gauss.

Claim 10

The process of claim 1 including the further step of monitoring the intensity of the emission spectra of one or more lines of nitrogen to determine the end point of said tungsten etch based on a rise in intensity of said nitrogen emission.

Claim 11

A process for plasma etching a tungsten layer on a semiconductor wafer through a patterned photoresist layer which is highly selective to photoresist and which will not laterally etch portions of said tungsten layer beneath said patterned photoresist layer, which process comprises: (a) flowing SF 6 , N 2 , and Cl 2 gases into an etch chamber containing said semiconductor wafer; 10 (b) maintaining a plasma in said chamber during said gas flow; and (c) immersing said wafer in said chamber wafer in a magnetic field; to thereby etch said tungsten layer while maintaining a good profile in said etched tungsten layer.

Claim 12

A process for plasma etching a tungsten layer on a semiconductor wafer through a patterned photoresist layer which is highly selective to photoresist and which will not laterally etch portions of said tungsten layer beneath said patterned photoresist layer, which process comprises: (a) flowing SF 6 , N 2 , and Cl 2 gases into an etch chamber containing said semiconductor wafer; 10 (b) maintaining a plasma in said chamber during said gas flow; and (c) immersing said wafer in said chamber wafer in a magnetic field; to thereby etch said tungsten layer while maintaining a good profile in said etched tungsten layer.

Claim 13

The process of claim 10 wherein the pressure in said chamber is maintained within a range of from about 10 to about 100 millitorr.

Claim 14

The process of claim 11 wherein said step of flowing said SF 6 into said etch chamber further comprises flowing said SF 6 gas into said chamber at a rate within a range of from about 50 to about 175 sccm.

Claim 15

The process of claim 12 wherein said step of flowing said N 2 into said etch chamber further comprises flowing said N 2 gas into said chamber at a rate within a range of from about 8 to about 12 volume percent of said SF 6 flow rate.

Claim 16

The process of claim 12 wherein said step of flowing said Cl 2 into said etch chamber further comprises flowing said Cl 2 gas into said chamber at a rate within a range of from about 8 to about 15 volume percent of said SF 6 flow rate.

Claim 17

The process of claim 10 wherein said step of maintaining said plasma in said etch chamber during said gas flow further comprises maintaining said plasma at a power level within a range of from about 150 to 300 watts.

Claim 18

The process of claim 10 wherein said step of immersing said wafer in said etch chamber in a magnetic field during said etch process further comprises immersing said wafer in a magnetic field having a magnetic moment lying in a plane parallel to the plane of said wafer.

Claim 19

The process of claim 16 wherein said step of immersing said wafer in said etch chamber in a magnetic field during said etch process further comprises rotating the magnetic moment of said magnetic field in a plane parallel to the plane of said wafer.

Claim 20

The process of claim 10 wherein said step of immersing said wafer in said etch chamber in a magnetic field during said etch process further comprises maintaining the field strength of said magnetic field within a range of from about 100 to about 150 gauss.

Claim 21

The process of claim 10 wherein the temperature of said wafer in said etch chamber doe not exceed 25° C. during said etch.

Claim 22

A process for plasma etching a tungsten layer on a semiconductor wafer through a patterned photoresist layer which is highly selective to photoresist and which will not laterally etch portions of said tungsten layer beneath said patterned photoresist layer, which process comprises: (a) flowing SF 6 , N 2 , and Cl 2 gases into an etch chamber containing said semiconductor wafer at flow rates within ranges of: (1) from about 50 to about 175 sccm of SF 6 ; (2) from about 2 to about 15 volume percent of said SF 6 flow rate of N 2 ; and (3) from about 2 to about 15 volume percent of said SF 6 flow rate of Cl 2 ; (b) maintaining a plasma in said chamber during said gas flow within a power range of from about 10 to about 300 watts; and (c) immersing said wafer in said chamber wafer in a magnetic field having a magnetic moment parallel to the plane of said wafer and a magnetic field strength of at least about 100 gauss; to thereby etch said tungsten layer while maintaining a good profile in said etched tungsten layer.

Claim 23

A process for plasma etching a tungsten layer on a semiconductor wafer through a patterned photoresist layer which is highly selective to photoresist and which will not laterally etch portions of said tungsten layer beneath said patterned photoresist layer, which process comprises: (a) flowing SF 6 , N 2 , and Cl 2 gases into an etch chamber containing said semiconductor wafer at flow rates within ranges of: (1) from about 50 to about 175 sccm of SF 6 ; (2) from about 2 to about 15 volume percent of said SF 6 flow rate of N 2 ; and (3) from about 2 to about 15 volume percent of said SF 6 flow rate of Cl 2 ; (b) maintaining a plasma in said chamber during said gas flow within a power range of from about 10 to about 300 watts; and (c) immersing said wafer in said chamber wafer in a magnetic field having a magnetic moment parallel to the plane of said wafer and a magnetic field strength of at least about 100 gauss; to thereby etch said tungsten layer while maintaining a good profile in said etched tungsten layer.

Claim 24

The process of claim 20 wherein the pressure in said chamber is maintained within a range of from about 10 to about 100 millitorr.

Claim 25

The process of claim 20 wherein the temperature of said wafer in said etch chamber doe not exceed 25° C. during said etch.

Claim 26

A process for plasma etching a tungsten layer on a semiconductor wafer through a patterned photoresist layer which is highly selective to photoresist and which will not laterally etch portions of said tungsten layer beneath said patterned photoresist layer, which process comprises: (a) flowing SF 6 at a rate within a range of from about 145 to about 155 sccm into an etch chamber containing said semiconductor wafer; (b) flowing N 2 into said chamber at a rate of from about 8 to about 12 volume percent of said SF 6 flow rate into said chamber; (c) flowing Cl 2 into said chamber at a rate of from about 8 to about 15 volume percent of said SF 6 flow rate into said chamber; (d) maintaining a plasma in said chamber during said gas flow within a power range of from about 150 to about 300 watts; (e) immersing said wafer in said chamber wafer in a magnetic field having a magnetic moment parallel to the plane of said wafer and a magnetic field strength within a range of from about 100 to about 150 gauss; and (f) rotating said magnetic moment in said plane parallel to the plane of said wafer during said etch; to thereby etch said tungsten layer while maintaining a good profile in said etched tungsten layer.

Claim 27

A process for plasma etching a tungsten layer on a semiconductor wafer through a patterned photoresist layer which is highly selective to photoresist and which will not laterally etch portions of said tungsten layer beneath said patterned photoresist layer, which process comprises: (a) flowing SF 6 at a rate within a range of from about 145 to about 155 sccm into an etch chamber containing said semiconductor wafer; (b) flowing N 2 into said chamber at a rate of from about 8 to about 12 volume percent of said SF 6 flow rate into said chamber; (c) flowing Cl 2 into said chamber at a rate of from about 8 to about 15 volume percent of said SF 6 flow rate into said chamber; (d) maintaining a plasma in said chamber during said gas flow within a power range of from about 150 to about 300 watts; (e) immersing said wafer in said chamber wafer in a magnetic field having a magnetic moment parallel to the plane of said wafer and a magnetic field strength within a range of from about 100 to about 150 gauss; and (f) rotating said magnetic moment in said plane parallel to the plane of said wafer during said etch; to thereby etch said tungsten layer while maintaining a good profile in said etched tungsten layer.

Claim 28

A process for plasma etching a tungsten layer on a semiconductor wafer through a patterned photoresist layer which is highly selective to photoresist and which will not laterally etch portions of said tungsten layer beneath said patterned photoresist layer, which process comprises: (a) flowing SF 6 , N 2 , and Cl 2 gases into an etch chamber containing said semiconductor wafer; (b) maintaining a plasma in said chamber during said gas flow; and (c) monitoring the intensity of the nitrogen emission spectra of one or more nitrogen lines for a rise in intensity of said nitrogen emission spectra to determine the endpoint of said etch; to thereby etch said tungsten layer while maintaining a good profile in said etched tungsten layer.

Claim 29

A process for plasma etching a tungsten layer on a semiconductor wafer through a patterned photoresist layer which is highly selective to photoresist and which will not laterally etch portions of said tungsten layer beneath said patterned photoresist layer, which process comprises: (a) flowing SF 6 , N 2 , and Cl 2 gases into an etch chamber containing said semiconductor wafer; (b) maintaining a plasma in said chamber during said gas flow; and (c) monitoring the intensity of the nitrogen emission spectra of one or more nitrogen lines for a rise in intensity of said nitrogen emission spectra to determine the endpoint of said etch; to thereby etch said tungsten layer while maintaining a good profile in said etched tungsten layer.