Multi level contact etch

A method of forming a memory cell, the method comprising:

• forming a plurality of conductive surfaces over a substrate;
• forming an etch stop layer (ESL) over the plurality of conductive surfaces;
• forming a dielectric layer over the ESL;
• forming a patterned hardmask layer over the dielectric layer;
• and
• forming a plurality of contact holes by etching the dielectric layer selectively to the ESL using the patterned hardmask layer as an etch mask, the plurality of contact holes being aligned such that each contact hole lands on a respective conductive surface of the plurality of conductive surfaces, the etching comprising
• flowing first and second fluorocarbons, dioxygen (O2), a diluent gas, and tungsten hexafluoride (WF6) to a plasma processing chamber, and
• exposing the substrate to a plasma generated in the plasma processing chamber while flowing the gases.

A method of processing a substrate, the method comprising:

• forming a patterned hardmask layer over a dielectric layer, the dielectric layer being over an etch stop layer (ESL), the ESL being conformal over a plurality of conductive surfaces of the substrate, each of the plurality of conductive surfaces being separated and at a different level from each other;
• and
• etching the dielectric layer selectively to the ESL using the patterned hardmask layer as an etch mask, the etching comprising
• exposing the substrate to a first plasma generated in a plasma processing chamber from a first process gas comprising a fluorocarbon, the exposing to the first plasma forming a plurality of recesses aligned with the plurality of conductive surfaces, and
• after one of the plurality of recesses reaches at a portion of the ESL disposed over an uppermost one of the plurality of conductive surfaces, exposing the substrate to a second plasma generated in the plasma processing chamber from a second process gas comprising the fluorocarbon, dioxygen (O2), and tungsten hexafluoride (WF6).