Inverting wafer and etching back plane to expose conductive pillars from back plane of wafer for further processing

A method for preparing a semiconductor structure, comprising:

• providing a wafer in which a plurality of conductive pillars are formed;
• inverting the wafer, and performing etching on a back plane of the wafer to expose each conductive pillar from the back plane of the wafer, wherein lengths of the plurality of conductive pillars exposed to the back plane are different;
• depositing an insulation layer on the back plane of the wafer and the conductive pillars, and depositing a filling layer on the insulation layer, wherein the filling layer completely covers back ends of the plurality of conductive pillars;
• and
• performing polishing on the filling layer and back ends of a part of the conductive pillars, until a back end of each conductive pillar is exposed and the back ends of the plurality of conductive pillars are flush with a back plane of the filling layer;
• wherein depositing the filling layer on the insulation layer comprises:
• coating a filling material on the insulation layer by a spin coating process;
• performing baking on the wafer;
• and
• performing an annealing process on the wafer, to enable the filling material to be solidified to form the filling layer;
• wherein the filling material comprises at least spin-on glass (SOG);
• wherein performing baking on the wafer comprises:
• heating the wafer to a first temperature value by a hot plate and performing baking for a first preset duration;
• heating the wafer to a second temperature value by the hot plate and performing baking for the first preset duration;
• and
• heating the wafer to a third temperature value by the hot plate and performing baking for the first preset duration;
• wherein the first temperature value is less than the second temperature value, the second temperature value is less than the third temperature value, and a difference between the second temperature value and the first temperature value is less than that between the third temperature value and the second temperature value.