1. Field of the Invention
The present invention relates to a method of forming a capacitor. More particularly, the present invention relates to a method for forming a stack capacitor by selective etching and static drying.
2. Description of the Prior Art
In dynamic random access memory (DRAM), two types of capacitors are conventionally used. One of the two is called the stack capacitor. In the process of forming the stack capacitor, first the rough shape of the capacitor is formed by dry etching. Then the sacrificial material filled in the capacitor is removed by a wet etching. Last, the remaining fluid is removed by spin-drying.
Under the trend of reducing the critical dimension, the aforementioned method encounters a lot of problems. First, the reduced critical dimension makes the capacitors closer, and the effective area on the capacitor structure is reduced. Second, as shown in FIG. 1, in the process of forming the rough capacitor by dry etching, a bulged part 100 appears at the collar of the capacitor column due to the characteristics of the reactive ion etching (RIE), this is called “bowing issue.” The bowing issue along with the smaller capacitor pitch makes the capacitor columns collapse and suffer damages easily during the spin-drying.
So it is necessary to provide a novel process for forming the stack capacitors to solve the problems.