Tunable structure profile
Provided are structures and methods for forming structures with sloping surfaces of a desired profile. An exemplary method includes performing a first etch process to differentially etch a gate material to a recessed surface, wherein the recessed surface includes a first horn at a first edge, a second horn at a second edge, and a valley located between the first horn and the second horn; depositing an etch-retarding layer over the recessed surface, wherein the etch-retarding layer has a central region over the valley and has edge regions over the horns, and wherein the central region of the etch-retarding layer is thicker than the edge regions of the etch-retarding layer; and performing a second etch process to recess the horns to establish the gate material with a desired profile.
1 . A method comprising:
performing a first etch process to differentially etch a gate material to a recessed surface, wherein the recessed surface includes a first horn at a first edge, a second horn at a second edge, and a valley located between the first horn and the second horn;
depositing an etch-retarding layer over the recessed surface, wherein the etch-retarding layer has a central region over the valley and has edge regions over the horns, and wherein the central region of the etch-retarding layer is thicker than the edge regions of the etch-retarding layer; and
performing a second etch process to recess the horns to establish the gate material with a desired profile.
2 . The method of claim 1 , further comprising:
forming a liner over the desired profile of the gate material, wherein the gate material and the liner form a gate;
forming a dielectric material over the gate; and
forming an interconnect in contact with the gate.
3 . The method of claim 1 , further comprising:
before performing the first etch process, depositing the gate material in a cavity over an active area; and
planarizing the gate material to define a planar upper surface of the gate material.
4 . The method of claim 1 wherein the etch-retarding layer is a polymer.
5 . The method of claim 1 , further comprising:
determining a desired threshold voltage for the gate material, wherein the desired profile of the gate material is selected based on the desired threshold voltage.
6 . The method of claim 1 , further comprising:
forming a liner over the desired profile of the gate material, wherein the gate material and the liner form a gate;
wherein the desired profile of the gate material comprises a sloped upper surface having a lowest point;
wherein the liner contacts the sloped upper surface along a gate interface having a gate interface area;
wherein a horizontal cross section of the gate material at the lowest point of the sloped upper surface has a cross-sectional area; and
wherein the gate interface area is greater than the cross-sectional area.
7 . The method of claim 6 , wherein the gate interface area is about 1.05 to about 1.4 times greater than the cross-sectional area.
8 . The method of claim 1 , further comprising:
forming a liner over the desired profile of the gate material, wherein the liner has a sloped top surface; and
forming an interconnect in contact with the sloped top surface of the liner at a contact interface extending from an upper end to a lower end and defining a contact interface area; wherein a horizontal cross-section of the interconnect at the upper end of the contact interface has an interconnect cross-sectional area, and wherein the contact interface area is greater than the interconnect cross-sectional area.
9 . The method of claim 8 , wherein the contact interface area is about 1.05 to about 1.4 times greater than the interconnect cross-sectional area.
10 . The method of claim 1 , wherein the etch-retarding layer is a polymer.
11 . The method of claim 1 , further comprising:
before performing the first etch process, depositing the gate material in a cavity over an active area; and
planarizing the gate material to define a planar upper surface of the gate material.
12 . The method of claim 1 , further comprising determining a desired threshold voltage for the gate material, wherein the desired profile of the gate material is selected based on the desired threshold voltage.
13 . The method of claim 1 , further comprising forming a liner over the desired profile of the gate material, wherein:
the gate material and the liner form a gate;
the desired profile of the gate material comprises a sloped upper surface having a lowest point;
the liner contacts the sloped upper surface along a gate interface having a gate interface area;
a horizontal cross section of the gate material at the lowest point of the sloped upper surface has a cross-sectional area; and
the gate interface area is greater than the cross-sectional area.
14 . The method of claim 13 , wherein the gate interface area is about 1.05 to about 1.4 times greater than the cross-sectional area.
15 . The method of claim 1 , further comprising:
forming a liner over the desired profile of the gate material, wherein the liner has a sloped top surface; and
forming an interconnect in contact with the sloped top surface of the liner at a contact interface extending from an upper end to a lower end and defining a contact interface area; wherein a horizontal cross-section of the interconnect at the upper end of the contact interface has an interconnect cross-sectional area, and wherein the contact interface area is greater than the interconnect cross-sectional area.
16 . The method of claim 15 , wherein the contact interface area is about 1.05 to about 1.4 times greater than the interconnect cross-sectional area.
17 . The method of claim 1 , wherein the first etch process is performed with BCl 3 /Cl 2 /O 2 gas, at a pressure of from 1 to 200 mTorr, at a power of from 400 to 1200 W, and with a bias of from 0 to 100 W.
18 . The method of claim 1 , wherein the etch-retarding layer is formed with a process performed with BCl 3 /CH 4 /HBr gas or SiCl 4 /O 2 /HBr gas, at a pressure of from 10 to 200 mTorr, at a power of from 400 to 1200 W, and with a bias of from 0 to 20 W.
19 . The method of claim 1 , wherein: the second etch process is performed with CF 4 /O 2 /N 2 , NF 3 /O 2 /N 2 , or BCl 3 /Cl 2 /O 2 gas, at a pressure of from 1 to 200 mTorr, at a power of from 400 to 1200 W, and with a bias of from 0 to 20 W.
20 . The method of claim 1 , wherein the thickness of the central region of the etch-retarding layer is at least 1.1 times greater than the thickness of the edge regions as measured at an interface of a dielectric layer and the gate material.