Heat treated coated article having glass substrate(s) and indium-tin-oxide (ITO) inclusive coating

An insulating glass unit (IGU), comprising:

• a first glass substrate;
• a plurality of layers sputter-disposed, directly or indirectly, on a first major surface of the first glass substrate, the plurality of layers including, in order moving away from the first glass substrate:
• a first layer comprising silicon oxynitride having an index of refraction of 1.5-2.1,
• a layer comprising ITO having an index of refraction of 1.7-2.1, and
• a second layer comprising silicon oxynitride having an index of refraction of 1.5-2.1;
• a second glass substrate in substantially parallel, spaced apart relation to the first glass substrate, the first major surface of the first glass substrate facing away from the second glass substrate when assembled;
• and
• an edge seal sealing together the first and second glass substrates,
• wherein the first glass substrate is heat treated with the plurality of layers disposed thereon, and
• wherein the first substrate with the plurality of layers on the first major surface of the first glass substrate has a hemispherical emissivity of less than or equal to about 0.20 and a sheet resistance less than or equal to about 20 ohms/square following said heat treating.