Composite cavity and forming method thereof

Abstract

There is provided a method for forming a composite cavity and a composite cavity formed using the method. The method comprises the following steps: providing a silicon substrate (); forming an oxide layer on the front side thereof; patterning the oxide layer to form one or more grooves (), the position of the groove () corresponding to the position of small cavity () to be formed; providing a bonding wafer (), which is bonded to the patterned oxide layer to form one or more closed micro-cavity structures () between the silicon substrate () and the bonding wafer (); forming a protective film () over the bonding wafer () and forming a masking layer () on the back side of the silicon substrate (); patterning the masking layer (), the pattern of the masking layer () corresponding to the position of a large cavity () to be formed; using the masking layer () as a mask, etching the silicon substrate () from the back side until the oxide layer at the front side thereof to form the large cavity () in the silicon substrate (); and using the masking layer () and the oxide layer as a mask, etching the bonding wafer () from the back side through the silicon substrate () until the protective film () thereover to form one or more small cavities () in the bonding wafer (). The uniformity of thickness of the semiconductor medium layer where the small cavity () in the composite cavity is located is well controlled by the present invention.