Device with modified work function layer and method of forming the same
A semiconductor device includes a plurality of fin structures disposed over a substrate and a work function alloy layer disposed over each fin structure of the plurality of fin structures. The plurality of fin structures includes a first fin structure and a second fin structure. A content of a first element in a first portion of the work function alloy layer, which portion is disposed over the first fin structure, is different from a content of the first element in a second portion of the work function alloy layer, which portion is disposed over the second fin structure.
1 . A method of making a semiconductor device, comprising
forming a plurality of fin structures on a substrate;
depositing a work function alloy layer over each fin structure of the plurality of fin structures, the work function alloy layer including a first element;
forming a first protective layer over a portion of the work function alloy layer above each fin structure of the plurality of fin structures other than a first portion of the work function alloy layer; and
reducing a content of the first element in the first portion of the work function alloy layer, wherein the first element is an etchable element and
reducing the content of the first element in the first portion of the work function alloy layer comprises wet etching the first portion of the work function alloy layer.
2 . The method of claim 1 , wherein the etchable element is Aluminum.
3 . The method of claim 2 , wherein the work function alloy layer comprises each of Ti, Al, N and C.
4 . The method of claim 2 , wherein the wet etching comprises exposing the first portion of the work function alloy layer to a basic solution.
5 . The method of claim 1 , further comprising removing the first protective layer.
6 . The method of claim 5 , wherein the removing the first protective layer comprises ashing the first protective layer.
7 . The method of claim 5 , wherein the plurality of fin structures further comprises at least one first fin structure and at least one second fin structure, wherein the first portion of the work function alloy layer is over the at least one first fin structure, and wherein the method further comprises:
forming a second protective layer over a portion of the work function alloy layer above each fin structure of the plurality of fin structures other than a second portion of the work function alloy layer, which second portion is above the at least one second fin structure; and
reducing a content of the first element in the second portion of the work function alloy layer, wherein the reduced content of the first element in the second portion of the work function alloy layer is different from the reduced content of the first element in the first portion of the work function alloy layer.
8 . The method of claim 1 , wherein the plurality of fin structures further comprises at least one first fin structure, wherein the first portion of the work function alloy layer is over the at least one first fin structure, and wherein forming the first protective layer comprises depositing a protective material over each fin structure of the plurality of fin structures, the protective material comprising a first portion which is above the at least one first fin structure, and a remaining portion which is above each fin structure of the plurality of fin structures other than the at least one fin structure;
depositing a mask over the remaining portion of the protective material; and
removing the first portion of the protective material, thereby exposing the at least one first fin structure, wherein the remaining portion of the protective material becomes the first protective layer.
9 . The method of claim 8 , wherein removing the first portion of the protective material comprises dry etching the first portion of the protective material.
10 . The method of claim 1 , comprising, for each fin structure of the plurality of fin structures, forming a protective layer over a portion of the work function alloy layer above each fin structure of the plurality of fin structures other than a portion of the work function alloy layer above the selected fin structure;
reducing a content of the first element in the portion of the work function alloy layer above the selected fin structure; and
removing the protective layer, wherein the reduced content of the first element in the respective portion of the work function alloy layer is different for each fin structure of the plurality of fin structures.
11 . The method of claim 10 , further comprising depositing a metal fill over the work function alloy layer, wherein for each fin structure of the plurality of fin structures, a portion of the metal fill and the respective portion of the work function alloy layer with the reduced content of the first element form an active gate structure of the respective fin structure of the plurality of the fin structures.
12 . A method of making a semiconductor device, comprising
forming a plurality of fin structures on a substrate, the plurality of fin structures including a first fin structure and a second fin structure;
depositing a work function alloy layer over each fin structure of the plurality of fin structures, the work function alloy layer containing a first element, the work function alloy layer comprising a first portion over the first fin structure and a second portion over the second fin structure; and
reducing a content of the first element in the first portion of the work function alloy layer without modifying a content of the first element in the second portion of the work function alloy layer, wherein the first element is Aluminum and the reducing the content of the first element in the first portion of the work function alloy layer comprises wet etching the first portion of the work function alloy layer.
13 . A method of making a semiconductor device, comprising
forming a plurality of fin structures on a substrate;
depositing a work function alloy layer over each fin structure of the plurality of fin structures, the work function alloy layer including a first element;
for each fin structure of the plurality of fin structures, forming a protective layer over a portion of the work function alloy layer above each fin structure of the plurality of fin structures other than a portion of the work function alloy layer above the selected fin structure;
reducing a content of the first element in the portion of the work function alloy layer above the selected fin structure; and
removing the protective layer, wherein the reduced content of the first element in the respective portion of the work function alloy layer is different for each fin structure of the plurality of fin structures.
14 . The method of claim 13 , further comprising depositing a metal fill over the work function alloy layer, wherein for each fin structure of the plurality of fin structures, a portion of the metal fill and the respective portion of the work function alloy layer with the reduced content of the first element form an active gate structure of the respective fin structure of the plurality of the fin structures.
15 . The method of claim 13 , wherein the first element is an etchable element and
reducing the content of the first element in the portion of the work function alloy layer above the selected fin structure comprises wet etching the portion of the work function alloy layer above the selected fin structure.
16 . The method of claim 15 , wherein the etchable element is Aluminum.
17 . The method of claim 16 , wherein the work function alloy layer comprises each of Ti, Al, N and C.
18 . The method of claim 15 , wherein the wet etching comprises exposing the portion of the work function alloy layer above the selected fin structure to a basic solution.
19 . The method of claim 13 , wherein the removing the protective layer comprises ashing the protective layer.
20 . The method of claim 13 , wherein the plurality of fin structures further comprises at least one first fin structure, and wherein forming the protective layer comprises depositing a protective material over each fin structure of the plurality of fin structures, the protective material comprising a first portion which is above the at least one first fin structure, and a remaining portion which is above each fin structure of the plurality of fin structures other than the at least one fin structure;
depositing a mask over the remaining portion of the protective material; and
removing the first portion of the protective material, thereby exposing the at least one first fin structure, wherein the remaining portion of the protective material becomes the first protective layer.