Method for fabricating a MOS transistor with two-layer inverse-T tungsten gate structure
First Claim
1. A method for fabricating a refractory metal gate electrode for a MOS transistor, comprising the steps of:
- depositing a first layer of refractory metal having a first density on a gate oxide layer formed on a silicon substrate;
depositing a second layer of refractory metal having a second density on said first layer of refractory metal;
wherein said first density is lower than said second density;
etching said second layer to form an upper gate electrode portion; and
,partially etching a thickness of said first layer to form a lower portion of said gate electrode that extends laterally beyond said upper gate electrode portion.
0 Assignments
0 Petitions
Accused Products
Abstract
The present invention is directed to a unique method for fabricating a silicon based MOS transistor having an inverse-T refractory metal gate structure. The gate fabricated according to this invention comprises a main CVD tungsten portion and a lower sputtered tungsten portion outwardly extending from the bottom of the CVD portion such that a cross section of the gate appears as an inverted "T". A Cl2 /O2 plasma etch is used to etch the CVD tungsten layer and a chemical etch is used to etch the sputtered tungsten layer to form the gate electrode. It has been discovered that sputtered tungsten is more resistant to Cl2 /O2 reactive ion etch than is CVD tungsten. The sputtered tungsten layer acts as a shield to protect the underlying gate oxide layer from ion damage throughout the fabrication process.
45 Citations
11 Claims
-
1. A method for fabricating a refractory metal gate electrode for a MOS transistor, comprising the steps of:
-
depositing a first layer of refractory metal having a first density on a gate oxide layer formed on a silicon substrate; depositing a second layer of refractory metal having a second density on said first layer of refractory metal;
wherein said first density is lower than said second density;etching said second layer to form an upper gate electrode portion; and
,partially etching a thickness of said first layer to form a lower portion of said gate electrode that extends laterally beyond said upper gate electrode portion. - View Dependent Claims (2, 3, 8, 9, 10, 11)
-
-
4. A method for fabricating a refractory metal gate electrode for a MOS transistor, comprising the steps of:
-
depositing a first layer of refractory metal having a first density on a gate oxide layer formed on a silicon substrate; depositing a second layer of refractory metal having a second density on said first layer of refractory metal;
wherein said first density is lower than said second density, wherein said first layer of refractory metal is deposited by sputter deposition and said second layer of refractory metal is deposited by chemical vapor deposition;etching said second layer to form an upper gate electrode portion; and
,partially etching a thickness of said first layer to form a lower portion of said gate electrode that extends laterally beyond said upper gate electrode portion.
-
-
5. A method for fabricating a tungsten gate electrode for a MOS transistor, comprising the steps of:
-
depositing a first layer of tungsten having a first density on a gate oxide layer formed on a silicon substrate; depositing a second layer of tungsten having a second density on said first layer of tungsten metal;
wherein said first density is lower than said second density;etching said second layer to form an upper gate electrode portion; and
,partially etching a thickness of said first layer to form a lower portion of said gate electrode that extends laterally beyond said upper gate electrode portion, wherein said second tungsten layer is etched by Cl2 /O2 plasma, said first tungsten layer acting to stop said Cl2 /O2 plasma etch.
-
-
6. A method for fabricating a tungsten gate electrode for a MOS transistor, comprising the steps of:
-
depositing a first layer of tungsten having a first density on a gate oxide layer formed on a silicon substrate; depositing a second layer of tungsten having a second density on said first layer of tungsten metal;
wherein said first density is lower than said second density;etching said second layer to form an uppergate electrode portion; and
,partially etching a thickness of said first layer to form a lower portion of said gate electrode that extends laterally beyond said upper gate electrode portion, wherein said first tungsten layer is etched by wet chemical etch. - View Dependent Claims (7)
-
Specification