Lateral etching of silicon

A method of processing a substrate, the method comprising:

• forming a recess over a substrate, the substrate comprising a layer stack of alternating layers of silicon (Si) layers and silicon-germanium (SiGe) layers, the recess exposing sidewalls of the Si layers and sidewalls of the SiGe layers;
• forming passivation layers on surfaces of the SiGe layers, the surfaces comprising the exposed sidewalls of the SiGe layers, the forming comprising
• flowing a first component gas into a plasma processing chamber,
• generating a first plasma within the plasma processing chamber, and
• exposing the substrate to the first plasma;
• and
• laterally etching a portion of the Si layers to form indents between the SiGe layers, the laterally etching comprising
• flowing a second component gas into the plasma processing chamber,
• generating a second plasma within the plasma processing chamber,
• exposing the substrate to the second plasma, and
• wherein the second plasma is different from the first plasma, and
• wherein the passivation layers inhibit an etching of the SiGe layers by the second plasma.

A method of processing a substrate, the method comprising:

• forming a plurality of vertical recesses in a layer stack, the layer stacking being disposed over the substrate, the layer stack comprising alternating layers of a nanosheet layer comprising germanium (Ge) and a sacrificial layer comprising silicon (Si), the substrate further comprising a dummy gate formed over the layer stack, the plurality of vertical recesses exposing sidewalls of the nanosheet layer and sidewalls of the sacrificial layer;
• exposing the substrate to a plasma comprising nitrogen within a plasma processing chamber to induce nitridation of a portion of surfaces of the nanosheet layer, the plasma being generated by flowing a first process gas comprising nitrogen to the plasma processing chamber;
• while maintaining the plasma and flowing the first process gas, pulsing a second process gas comprising fluorine to the plasma processing chamber to supply fluorine to the plasma, wherein the plasma supplied with fluorine laterally etches a portion of the sacrificial layer and forms a plurality of lateral recesses between adjacent nanosheets;
• depositing an inner sidewall spacer layer to fill the plurality of lateral recesses;
• and
• etching a portion of the inner sidewall spacer layer to expose tips of the nanosheets, the remaining portion of the inner sidewall spacer layer forming an inner sidewall spacer.