System and method for increasing electron density levels in a plasma of a substrate processing system

A method comprising:

• arranging a substrate on a substrate support within a substrate processing chamber;
• injecting an electronegative gas, a baseline electropositive gas, and an additional electropositive gas into the substrate processing chamber, wherein the electronegative gas includes an etch precursor, wherein the additional electropositive gas mixes with and increases electron density of a plasma in the substrate processing chamber, and
• wherein prior to injecting the electronegative gas, the baseline electropositive gas, and the additional electropositive gas into the substrate processing chamber, setting an amount, flow rate or pressure of the additional electropositive gas based on at least one of a pressure of the electronegative gas or an electron affinity level of the additional electropositive gas;
• decreasing a percentage of the electronegative gas relative to a total amount of gas supplied to the substrate processing system when (i) the additional electropositive gas is supplied, and (ii) a total amount of electropositive gas is increased;
• and
• striking the plasma to etch the substrate.