Method of profile control for semiconductor manufacturing
A method of forming a semiconductor structure includes forming a first mandrel layer over a target layer, forming a second mandrel layer over the first mandrel layer, and patterning a mandrel by etching the second mandrel layer and the first mandrel layer. The first mandrel layer has a first etch rate and the second mandrel layer has a second etch rate less than the first etch rate.
1 . A method of forming a semiconductor structure, the method comprising:
forming a first mandrel layer over a target layer, the first mandrel layer having a first etch rate;
forming a second mandrel layer over the first mandrel layer, the second mandrel layer having a second etch rate, the second etch rate being less than the first etch rate;
forming a third mandrel layer over the second mandrel layer, the third mandrel layer having a third etch rate, the third etch rate being less than the second etch rate; and
patterning a mandrel by etching the third mandrel layer, the second mandrel layer, and the first mandrel layer, wherein etching the third mandrel layer, the second mandrel layer, and the first mandrel layer comprises a reactive ion etch performed with a mixture of nitrogen and hydrogen.
2 . The method of claim 1 , wherein after patterning the mandrel, remaining portions of the first mandrel layer, the second mandrel layer, and the third mandrel layer have aligned sidewalls.
3 . The method of claim 1 , wherein after patterning the mandrel, a remaining portion of the third mandrel layer is wider than a remaining portion of the second mandrel layer and the remaining portion of the second mandrel layer is wider than a remaining portion of the first mandrel layer.
4 . The method of claim 1 , further comprising:
forming spacers adjacent to the mandrel; and
removing the mandrel with a mandrel pull etch process.
5 . The method of claim 4 , further comprising:
patterning the target layer using the spacers as a mask; and
forming a metallization pattern in trenches between remaining portions of the target layer.
6 . The method of claim 1 , wherein the first mandrel layer comprises silicon oxide, the second mandrel layer comprises silicon oxynitride, and the third mandrel layer comprises silicon nitride.
7 . The method of claim 1 , wherein etching the third mandrel layer, the second mandrel layer, and the first mandrel layer further comprises forming an organic layer on a vertical sidewall of the mandrel.
8 . A method of forming a semiconductor structure, the method comprising:
forming a mandrel layer over a target layer of a substrate, the target layer being over the substrate, the mandrel layer comprising a composition gradient from a first surface of the mandrel layer to a second surface of the mandrel layer, the composition gradient being between a higher concentration of a species at the second surface of the mandrel layer and a lower concentration of the species at the first surface of the mandrel layer, the species being nitrogen;
patterning a mandrel from the mandrel layer, a profile shape of the mandrel being controlled by the composition gradient of the mandrel layer;
forming a spacer on a sidewall of the mandrel;
removing the mandrel to leave the spacer; and
using the spacer as a mask to pattern the target layer.
9 . The method of claim 8 , wherein the profile shape of the mandrel is trapezoidal in a cross-sectional view, a top surface of the mandrel being broader than a bottom surface of the mandrel.
10 . The method of claim 8 , wherein the mandrel layer comprises silicon dioxide.
11 . The method of claim 8 , wherein the mandrel layer comprises amorphous silicon.
12 . The method of claim 8 , wherein patterning the mandrel from the mandrel layer comprises a reactive ion etch performed with a mixture of nitrogen and hydrogen.
13 . A method of forming a semiconductor structure, the method comprising:
placing a substrate in a deposition apparatus on a platter of a susceptor, the susceptor being a part of the deposition apparatus, a target layer being over the substrate;
forming a first mandrel layer over the target layer by performing a first atomic layer deposition (ALD) process while rotating the susceptor at a first rotational speed, the first mandrel layer comprising a composition gradient from a first surface of the first mandrel layer to a second surface of the first mandrel layer, the composition gradient being between a higher concentration of a species at the second surface of the first mandrel layer and a lower concentration of the species at the first surface of the first mandrel layer, the species being silicon;
forming a second mandrel layer over the target layer by performing a second ALD process while rotating the susceptor at a second rotational speed, the second rotational speed being less than the first rotational speed; and
forming a mandrel by patterning the second mandrel layer and the first mandrel layer.
14 . The method of claim 13 , wherein the first rotational speed is in a range of 1 rpm to 350 rpm.
15 . The method of claim 13 , wherein the first ALD process comprises a first precursor and the second ALD process comprises a second precursor, the second precursor being different from the first precursor.
16 . The method of claim 13 , wherein the first mandrel layer comprises titanium oxide.
17 . The method of claim 13 , wherein the first mandrel layer comprises aluminum oxide.
18 . The method of claim 13 , wherein a profile shape of the mandrel is trapezoidal in a cross-sectional view.
19 . The method of claim 13 , wherein a profile shape of the mandrel is oblong-shaped in a cross-sectional view.
20 . The method of claim 13 , wherein a top surface of the mandrel is broader than a bottom surface of the mandrel.