Patent ID: 6518164
Filing Date: 2003-02-11
Classification: H01L

Abstract:
A method for forming a plurality of contact windows and a via hole of a dynamic random access memory, the method comprising:providing a semiconductor substrate, a first oxide layer is formed on said semiconductor substrate, a nitride layer is formed on said first oxide layer and a second oxide layer is formed on said nitride layer, wherein a first polysilicon region is embedded in said first oxide layer on said semiconductor substrate, a second polysilicon region is embedded in said nitride layer on said first oxide layer, and a third polysilicon region is embedded in said second oxide layer on said nitride layer; forming a patterned photoresist layer on the surface of said second oxide layer; providing an etchant that is a mixing gas with a C4F6/CH2F2/CF4/Ar/O2 gas; performing a dry etching process one time by way of using said patterned photoresist layer as an etching mask and said etchant to etch through in turn said second oxide layer, said nitride layer and said first oxide layer until forming a first trench with a aspect ratio on said semiconductor substrate that is located between said first polysilicon region and said second polysilicon region, and a second trench with a second aspect ratio is formed on said first polysilicon region, a third trench with a third aspect ratio is formed on the second polysilicon region, and a fourth trench with a fourth aspect ratio is formed on the third polysilicon region; and removing said photoresist layer to form a via hole with a vertical profile in said first trench, a first contact window with a vertical profile in said second trench, a second contact window with a vertical profile in said third trench and a third contact window with a vertical profile in said fourth trench.