Multi-layer photo etching mask including organic and inorganic materials
A method includes forming an etching mask, which includes forming a bottom anti-reflective coating over a target layer, forming an inorganic middle layer over the bottom anti-reflective coating, and forming a patterned photo resist over the inorganic middle layer. The patterns of the patterned photo resist are transferred into the inorganic middle layer and the bottom anti-reflective coating to form a patterned inorganic middle layer and a patterned bottom anti-reflective coating, respectively. The patterned inorganic middle layer is then removed. The target layer is etched using the patterned bottom anti-reflective coating to define a pattern in the target layer.
1. A method comprising:
forming an oxide layer over a semiconductor region;
depositing a high-k dielectric layer over the oxide layer;
depositing first work-function layer over the high-k dielectric layer;
forming a tetra-layer etching mask comprising four layers, wherein the tetra-layer comprises:
a first layer, a second layer over the first layer, a third layer over the second layer, and a fourth layer over the third layer;
forming a patterned photoresist over the tetra-layer etching mask;
transferring patterns of the patterned photoresist into the tetra-layer etching mask; and
etching a portion of the first work-function layer using a remaining portion of the tetra-layer etching mask to define a pattern in the first work-function layer, wherein the remaining portion of the tetra-layer etching mask comprises the first layer and the second layer, and wherein at a first time the etching the portion of the first work-function layer is started, a top surface of the second layer is exposed, wherein the etching is performed using the high-k dielectric layer as an etch stop layer.
2. The method of claim 1 , wherein the tetra-layer etching mask comprises two inorganic layers and two organic layers formed alternatingly.
3. The method of claim 2 , wherein the two inorganic layers comprise a same inorganic material.
4. The method of claim 3 , wherein the two inorganic layers comprise metal oxides.
5. The method of claim 4 , wherein the two inorganic layers comprise aluminum oxide layers.
6. The method of claim 1 , wherein at a second time the etching the portion of the first work-function layer is ended, the second layer remains.
7. The method of claim 1 , wherein after the first work-function layer is etched, an additional portion of the high-k dielectric layer underlying the etched portion of the first work-function layer is revealed.
8. The method of claim 1 further comprising:
removing remaining portions of the tetra-layer etching mask; and
depositing a second work-function layer over the high-k dielectric layer and an additional remaining portion of the first work-function layer.
9. The method of claim 1 further comprising, before the etching the portion of the first work-function layer, removing two upper layers of the tetra-layer etching mask, with the remaining portion of the tetra-layer etching mask comprising two lower layers of the tetra-layer etching mask.
10. The method of claim 1 further comprising:
removing a first dummy gate to form a first trench; and
removing a second dummy gate to form a second trench, wherein the first work-function layer comprises a first portion and a second portion extending into the first trench and the second trench, respectively, and wherein during the etching the first work-function layer, the first portion is etched, and the second portion is left un-etched.
11. A method comprising:
forming an etching mask comprising a first portion and a second portion in a first region and a second region, respectively, wherein the forming the etching mask comprises:
depositing a first metal oxide layer;
forming a bottom layer over the first metal oxide layer;
depositing a middle layer over the bottom layer, wherein the middle layer comprises a second metal oxide; and
forming an upper layer over the middle layer;
forming a patterned photoresist over the upper layer;
etching the etching mask using the patterned photoresist to define patterns;
removing the patterned photoresist;
removing the upper layer and the middle layer; and
etching a target layer underlying the first metal oxide layer, wherein the bottom layer defines patterns of the target layer, wherein the target layer comprises a first work-function layer, and wherein the etching stops on a top surface of a high-k dielectric layer underlying the target layer.
12. The method of claim 11 , wherein in the etching the target layer, a first portion of the first work-function layer in the first region is removed, and a second portion of the first work-function layer in the second region remains.
13. The method of claim 12 further comprising depositing a second work-function layer in the first region and the second region, wherein the second work-function layer is over the second portion of the first work-function layer.
14. The method of claim 11 , wherein the forming the bottom layer comprises forming a cross-linked photoresist.
15. The method of claim 11 , wherein the forming the upper layer comprises forming a cross-linked photoresist, and wherein the patterned photoresist is in physical contact with the upper layer.
16. The method of claim 11 , wherein both of the middle layer and the first metal oxide layer comprise aluminum oxide.
17. The method of claim 13 , wherein the second work-function layer physically contacts the top surface of the high-k dielectric layer to form a horizontal interface.
18. A method comprising:
forming a high-k dielectric layer over a semiconductor fin;
depositing a first work-function layer over the high-k dielectric layer;
forming an etching mask comprising:
depositing a first inorganic mask layer;
depositing a first organic mask layer over the first inorganic mask layer;
depositing a second inorganic mask layer over the first organic mask layer; and
depositing a second organic mask layer over the second inorganic mask layer;
patterning the etching mask;
etching the first work-function layer to reveal the high-k dielectric layer, with a part of the patterned etching mask remaining; and
depositing a second work-function layer over the high-k dielectric layer and a remaining portion of the first work-function layer.
19. The method of claim 18 , wherein the first inorganic mask layer and the second inorganic mask layer comprise an amphoteric material.
20. The method of claim 18 , wherein the etching mask is patterned using a photoresist that is formed over the etching mask.