Tin oxide films in semiconductor device manufacturing

A method of processing a substrate, the method comprising:

• (a) providing a substrate having one or more mandrels comprising a mandrel material, wherein a layer of a spacer material coats horizontal surfaces and sidewalls of the one or more mandrels;
• and
• (b) etching and completely removing the layer of the spacer material from the horizontal surfaces of the one or more mandrels and thereby exposing the mandrel material, without completely removing the spacer material residing at the sidewalls of the one or more mandrels, wherein the etching comprises exposing the substrate to a plasma formed using a mixture comprising a first gas and a polymer-forming gas, and wherein the etching comprises forming a polymer on the substrate,
• wherein the etching is performed in a plasma processing apparatus, the plasma processing apparatus comprising a first sub-chamber configured to receive a process gas and a second sub-chamber having a substrate support configured to support the substrate, wherein the plasma processing apparatus comprises an induction coil disposed about the first sub-chamber, and a bias electrode disposed in the substrate support;
• and
• wherein the etching comprises:
• (i) placing the substrate onto the substrate support in the second sub-chamber;
• (ii) admitting the process gas into the first sub-chamber, the process gas comprising the first gas and the polymer-forming gas;
• (iii) providing RF power to the induction coil to generate a first plasma from the process gas, to generate a first mixture comprising one or more first species;
• (iv) filtering the one or more first species to generate a filtered mixture;
• (v) providing RF power to the bias electrode to generate a second plasma in the filtered mixture in the second sub-chamber to generate a second mixture, the second mixture comprising one or more second species;
• and
• (vi) exposing the substrate to the second mixture to etch the spacer material from the horizontal surfaces of the one or more mandrels and to form the polymer on the substrate.