PLASMA ETCHING CARBONACEOUS LAYERS WITH SULFUR-BASED ETCHANTS

• US 20090212010A1
• Filed: 02/21/2008
• Published: 08/27/2009
• Est. Priority Date: 02/21/2008
• Status: Active Grant

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Zhou, Jie, Hsieh, Chang-Lin, Liao, Bryan, Ma, Shawming, Wang, Judy, Kim, Hun Sang
• Granted Patent: US 8,133,819 B2
• Time in Patent Office: Days
• US Class Current: 216/47
• CPC Class Codes: H01L 21/31116 by dry-etching
• CPC Class Codes: H01L 21/31138 by dry-etching

Abstract

Etching of carbonaceous layers with an etchant gas mixture including molecular oxygen (O₂) and a gas including a carbon sulfur terminal ligand. A high RF frequency source is employed in certain embodiments to achieve a high etch rate with high selectivity to inorganic dielectric layers. In certain embodiments, the etchant gas mixture includes only the two components, COS and O₂, but in other embodiments additional gases, such as at least one of molecular nitrogen (N₂), carbon monoxide (CO) or carbon dioxide (CO₂) may be further employed to etch to carbonaceous layers.

Claims

1. A method of etching a feature in a carbonaceous layer comprising at least 20 wt % carbon, the method comprising:

providing a substrate including a patterned photoresist layer disposed above the carbonaceous layer;

loading the substrate into a plasma etch chamber;

introducing an etchant gas mixture including O₂ and a gas comprising a carbon sulfur terminal ligand into the plasma etch chamber;

etching the carbonaceous layer with a plasma of the etchant gas mixture.

2. The method of claim 1, wherein the etch gas mixture is energized with a high frequency RF source having a RF frequency above 100 MHz.

3. The method of claim 1, wherein the carbonaceous layer is an amorphous carbon layer comprising at least 50 wt % carbon.

4. The method of claim 1, wherein the gas comprising a carbon sulfur terminal ligand is selected from the group consisting of:

COS, SCOR₂, SCORNR₂, SCR₂, SCRNR₂, SC(NR)₂, SCNR, SC(OR)₂, wherein R is one of an alkyl group, an aryl group, or hydrogen.

5. The method of claim 1, wherein the gas comprising a carbon sulfur terminal ligand is carbonyl sulfide (COS) and a COS:

O₂ volumetric flow rate ratio is between about 0.25 and about 1.0.

6. The method of claim 1, wherein the etchant gas mixture consists essentially of COS and O₂.

7. The method of claim 1, wherein the etchant gas mixture further comprises at least one of N₂, O₃, H₂O, H₂O₂, CO or CO₂.

8. The method of claim 1, wherein the etchant gas mixture is energized with a high frequency RF generator having a frequency above 100 MHz and with one or more low frequency RF generator having a frequency below 60 MHz, wherein the one or more low frequency generator delivers less than half as much power to the plasma as that of the high frequency RF generator.

9. The method of claim 1, wherein the etchant gas mixture is delivered to the plasma etch chamber with a higher gas flow rate at a first gas inlet proximate to the substrate center than at a second gas inlet proximate to the substrate periphery while the plasma is exposed to a higher magnetic field proximate to the substrate center than proximate to the substrate periphery to improve uniformity of the carbonaceous layer etch.

10. The method of claim 1, further comprising:

controlling the temperature of the substrate at a point proximate to the substrate center at a first setpoint while controlling the temperature of the substrate at a point proximate to the substrate periphery at a second setpoint, different than the first to improve uniformity of the carbonaceous layer etch.

11. The method of claim 1, further comprising:

etching the carbonaceous layer with a first etch step with the plasma including the gas comprising the carbon sulfur terminal ligand; and

etching the carbonaceous layer with a second etch step, subsequent to the first etch step, the second etch step providing a plasma of an etchant gas mixture comprising N₂ and O₂ and substantially free of the gas comprising the carbon sulfur terminal ligand.

12. A method of etching an amorphous carbon layer comprising at least 50 wt % carbon, comprising:

providing a substrate including a multi-layered mask on a substrate layer, the multi-layered mask comprising;

the amorphous carbon layer disposed on the substrate layer;

an inorganic dielectric cap layer disposed on the amorphous carbon layer;

and a patterned photoresist layer disposed over the inorganic dielectric cap layer;

loading the substrate into a plasma etch chamber;

introducing an etchant gas mixture including O₂ and a gas comprising a carbon sulfur terminal ligand into the plasma etch chamber;

etching the amorphous carbon layer with a plasma of the etchant gas mixture.

13. The method of claim 12, wherein the etch gas mixture is energized with a high frequency RF source having an RF frequency above 100 MHz.

14. The method of claim 12, wherein the gas comprising a carbon sulfur terminal ligand is carbonyl sulfide (COS) and a COS:

O₂ volumetric flow rate ratio is between about 0.25 and about 1.0.

15. The method of claim 12, further comprising:

etching the inorganic dielectric cap layer with a fluorocarbon gas energized with one or more low frequency RF generators having a frequency below about 60 MHz without applying high frequency RF energy having a frequency above about 100 MHz to the plasma;

purging the plasma etch chamber of the fluorocarbon gas; and

etching the amorphous carbon layer with the etchant gas mixture energized with a high frequency RF generator having a frequency above about 100 MHz.

16. The method of claim 15, wherein the etchant gas mixture energized with the high frequency RF generator is further energized with the one or more low frequency RF generator, wherein the one or more low frequency generator delivers less than half as much power to the plasma as that of the high frequency RF generator.

17. The method of claim 12, further comprising:

etching the substrate layer with a fluorocarbon gas; and

stripping the amorphous carbon layer with a plasma energized with the high frequency RF generator after etching the substrate layer.

18. A computer-readable medium having stored thereon a set of machine-executable instructions which, when executed by a data-processing system, cause a system to perform a method comprising:

providing a substrate including a patterned photoresist layer disposed above an amorphous carbon layer comprising at least 50 wt % carbon;

loading the substrate into a plasma etch chamber;

introducing an etchant gas mixture including O₂ and a gas comprising a carbon sulfur terminal ligand into the plasma etch chamber;

etching the amorphous carbon layer with a plasma of the etchant gas mixture.

19. The computer-readable medium of claim 18, wherein the etchant gas mixture is energized with a high frequency RF source having an RF frequency above 100 MHz.

20. The computer-readable medium of claim 18, wherein the gas comprising a carbon sulfur terminal ligand is carbonyl sulfide (COS) and wherein the instructions cause the system to introduce COS to the plasma etch chamber at a volumetric flow rate ratio between about 0.25 and about 1.0.