PLASMA MEDIATED ASHING PROCESSES
Plasma mediated ashing processes for removing organic material from a substrate generally includes exposing the substrate to the plasma to selectively remove photoresist, implanted photoresist, polymers and/or residues from the substrate, wherein the plasma contains a ratio of active nitrogen and active oxygen that is larger than a ratio of active nitrogen and active oxygen obtainable from plasmas of gas mixtures comprising oxygen gas and nitrogen gas. The plasma exhibits high throughput while minimizing and/or preventing substrate oxidation and dopant bleaching. Plasma apparatuses are also described.
1 . A plasma ashing process for removing photoresist, polymers and/or residues from a substrate, the process comprising:
placing the substrate including the photoresist, polymers, and/or residues into a reaction chamber;
generating a plasma from a gas mixture comprising NH 3 , wherein the NH 3 constitutes a major portion of the gas mixture; and
exposing the substrate to the plasma to selectively remove the photoresist, polymers, and/or residues from the substrate.
2 . The plasma ashing process of claim 1 , wherein the gas mixture further comprises a forming gas mixture consisting of hydrogen gas (H 2 ) and nitrogen gas (N 2 ).
3 . The plasma ashing process of claim 1 and 2 , wherein the gas mixture further comprises oxygen gas (O 2 ).
4 . The plasma ashing process of claim 1 and 2 , wherein the oxygen gas (O 2 ) is less than or equal to 10% of the gas mixture by volume.
5 . The plasma ashing process of claim 1 , wherein the gas mixture further comprises nitrogen (N 2 ).
6 . The plasma ashing process of claim 1 , wherein the gas mixture further consists essentially of the NH 3 .
7 . The plasma ashing process of claim 1 , wherein said process includes exposing said gas mixture to a catalyst for enhancing formation of active nitrogen.
8 . The plasma ashing process of claim 1 , wherein said process includes inputting a gas additive to said gas mixture for enhancing formation of active nitrogen.
9 . The plasma ashing process of claim 1 , wherein said process comprises generating the plasma in a plasma tube formed of quartz.
10 . The plasma ashing process of claim 1 , wherein said process includes passing said plasma through a filter for reducing the amount of active oxygen in said gas mixture.
11 . The plasma ashing process of claim 1 , wherein said process includes exposing said plasma to a gettering agent for reducing the amount of active oxygen in said gas mixture.
12 . The plasma ashing process of claim 1 , wherein said process includes decreasing a chamber pressure housing said plasma and the substrate for enhancing formation of active nitrogen.
13 . The plasma ashing process of claim 1 , wherein said plasma generating step includes exposing said gas mixture to electromagnetic energy for generating said plasma.
14 . The plasma ashing process of claim 1 , wherein said plasma generating step includes exposing said gas mixture to microwave energy for generating said plasma.
15 . The plasma ashing process of claim 1 , wherein the exposing the substrate to the plasma comprises removing charged particles such that the substrate is exposed to electrically neutral species.
16 . The plasma ashing process of claim 1 , wherein generating the plasma comprises microwave excitation at a power setting of 1000 to 10000 watts.
17 . The plasma ashing process of claim 1 , wherein the substrate is a 300 mm wafer and generating the plasma comprises microwave excitation at a power setting of 2000 to 10000 watts.
18 . The plasma ashing process of claim 1 , wherein generating the plasma comprises a total gas flow rate of less than 10 standard liters per minute.
19 . The plasma ashing process of claim 1 , wherein the substrate is a 300 mm wafer and generating the plasma comprises a total gas flow rate of less than 5 standard liters per minute.
20 . The plasma ashing process of claim 1 , wherein the substrate is a 300 mm wafer, the gas mixture consists of NH 3 and less than 10% oxygen, and generating the plasma comprises microwave excitation of the gas mixture at a power setting of 2000 to 10000 watts.
21 . The plasma ashing process of claim 1 , wherein exposing the substrate to the plasma to selectively remove the photoresist, polymers, and/or residues from the substrate is during front end of line processing.
22 . The plasma ashing process of claim 1 , wherein removing the photoresist, polymers, and/or residues is immediately after an ion implantation step.
23 . The plasma ashing process of claim 1 , wherein the pressure in the reaction chamber is between 0.1 Torr to 4 Torr.
24 . A process for ashing organic matter from a substrate, comprising:
generating a plasma from a gas mixture comprising NH 3 and O 2 , wherein the NH 3 is at least 40% of the gas mixture;
exposing the substrate having the organic matter thereon to the plasma; and
selectively removing the organic matter from the substrate.
25 . The process of claim 24 , wherein the organic matter comprises implanted photoresist having a crosslinked upper portion and a non-crosslinked lower portion; photoresist, polymers, residues, and mixtures thereof.
26 . The plasma ashing process of claim 24 , wherein the substrate is a 300 mm wafer; the gas mixture consists of NH 3 and less than 10% oxygen; and generating the plasma comprises microwave excitation of the gas mixture at a power setting of 2000 to 10000 watts.
27 . The plasma ashing process of claim 24 , wherein generating the plasma comprises microwave excitation at a power setting of 1000 to 10000 watts.
28 . The plasma ashing process of claim 24 , wherein the substrate is a 300 mm wafer and generating the plasma comprises microwave excitation at a power setting of 2000 to 10000 watts.
29 . The plasma ashing process of claim 24 , wherein generating the plasma comprises a total gas flow rate of less than 10 standard liters per minute.
30 . The plasma ashing process of claim 24 , wherein the substrate is a 300 mm wafer; and generating the plasma comprises a total gas flow rate of less than 5 standard liters per minute.
31 . A plasma ashing process for removing a photoresist layer from a substrate, wherein the photoresist layer includes an upper portion and a lower portion, the upper portion having a higher crosslinked density than the lower portion, the plasma ashing process comprising:
removing substantially all of the upper portion by exposing the photoresist layer to a low density plasma of less than about 70 W/cm 3 formed from a gas mixture comprising NH 3 , wherein the NH 3 constitutes a major portion of the gas mixture; and
removing the lower portion by exposing the photoresist layer to a high density plasma of at least about 70 W/cm 3 formed from a gas mixture comprising NH 3 , wherein the NH 3 constitutes a major portion of the gas mixture.
32 . The plasma ashing process of claim 31 , wherein the gas mixture for removing the lower portion further comprises oxygen gas.
33 . The plasma ashing process of claim 31 , further comprising passivating the surface with a plasma formed of a gas mixture free of NH 3 .
34 . The plasma ashing process of claim 31 , further comprising exposing the substrate to a plasma effective to remove photoresist residues, wherein the plasma is formed from a gas mixture free of NH 3 .