Method for etching silicon wafer

A method for etching a silicon wafer, comprising:

• a main etching process using a first mixed gas to perform a plasma etching process to etch the silicon wafer until a pattern on the silicon wafer reaches a specified aspect ratio, the first mixed gas being configured to etch silicon and react with silicon to form non-volatile reaction products;
• and
• an auxiliary etching process using a second mixed gas to perform another plasma etching process, the second mixed gas being configured to react with silicon to generate the non-volatile reaction products, and a formation rate of the non-volatile reaction products in the auxiliary etching process being greater than a formation rate of the non-volatile reaction products in the main etching process;
• wherein:
• the main etching process and the auxiliary etching process are alternately performed at least once until the pattern on the silicon wafer reaches a specified etching depth;
• the specified etching depth is smaller than a target etching depth;
• after the pattern on the silicon wafer reaches the specified etching depth, the main etching process is performed until the pattern on the silicon wafer reaches the target etching depth;
• the first mixed gas includes sulfur hexafluoride, and one or more of oxygen, hydrogen bromide, silicon tetrafluoride, and silicon tetrachloride;
• the second mixed gas includes one or more of oxygen, hydrogen bromide, silicon tetrafluoride, and silicon tetrachloride;
• if the first mixed gas and the second mixed gas contain exactly the same gas types in the four gases of oxygen, hydrogen bromide, silicon tetrafluoride, and silicon tetrachloride, a flow rate of each gas included in the four gases in the first mixed gas is smaller than the flow rate of the same gas included in the four gases in the second mixed gas;
• and
• if the gas types contained in the first mixed gas and the second mixed gas are at least partially different in the four gases of oxygen, hydrogen bromide, silicon tetrafluoride, and silicon tetrachloride, a total flow rate of these four gases in the first mixed gas is less than a total flow rate of these four gases in the second mixed gas.