Patent ID: 6287974
Filing Date: 2001-09-11
Classification: H01L

Abstract:
In a plasma processing chamber, a method of etching a trench in a silicon layer, said silicon layer being disposed below an oxide layer, said oxide layer being disposed below a nitride layer, said nitride layer being disposed below a photoresist mask, said method comprising:flowing a first etchant source gas into said plasma processing chamber;forming a first plasma from said first etchant source gas;etching substantially through said nitride layer with said first plasma;evacuating said first etchant source gas from said plasma processing chamber;thereafter flowing a second etchant source gas into said plasma processing chamber;forming a second plasma from said second etchant source gas; andetching through said oxide layer and a portion of said silicon layer with said second plasma, wherein said etching with said second plasma is extended for a period of time after said pad oxide layer is etched through, said period of time being sufficiently long to form an effective top-rounded feature on a portion of said trench.