Methods to reduce the critical dimension of semiconductor devices and related semiconductor devices
A method of forming features on a target layer. The features have a critical dimension that is triple- or quadruple-reduced compared to the critical dimension of portions of a resist layer used as a mask. An intermediate layer is deposited over a target layer and the resist layer is formed over the intermediate layer. After patterning the resist layer, first spacers are formed on sidewalls of remaining portions of the resist layer, masking portions of the intermediate layer. Second spacers are formed on sidewalls of the portions of the intermediate layer. After removing the portions of the intermediate layer, the second spacers are used as a mask to foil the features on the target layer. A partially fabricated integrated circuit device is also disclosed.
1. A method of forming features on a target layer, comprising:
forming openings in a resist layer having a first thickness located above an intermediate layer on a target layer;
forming a first set of spacers on sidewalls of the resist layer, the first set of spacers including a first material and having a second thickness at least one third the first thickness of the resist layer;
removing portions of the resist layer and the intermediate layer not masked by the first set of spacers;
exposing portions of the target layer except for portions masked by the first set of spacers;
removing the first set of spacers;
exposing remaining portions of the intermediate layer;
forming second spacers on sidewalls of the remaining portions of the intermediate layer such that a first portion of the second spacers are separated from first neighboring second spacers by a distance equal to a width of the second spacers, a second portion of the second spacers are separated from second neighboring second spacers by voids and the remaining portions of the intermediate layer, and a third portion of the second spacers are separated from third neighboring second spacers by the remaining portions of the intermediate layer on both sides of the third portion of the second spacers;
removing the remaining portions of the intermediate layer; and
forming features in exposed portions of the target layer, the features having a critical dimension about equal to the second thickness of the first set of spacers.
2. The method of claim 1 , wherein forming the second spacers on the sidewalls of the remaining portions of the intermediate layer comprises forming the second spacers from the first material.
3. The method of claim 1 , further comprising selecting the intermediate layer to be selectively etchable relative to the first material.
4. The method of claim 1 , further comprising forming an anti-reflective layer between the resist layer and the intermediate layer.
5. The method of claim 1 , wherein removing the portions of the resist layer and the intermediate layer not masked by the first set of spacers comprises creating an opening having a distance of about three times the thickness of the first spacers between some of the remaining portions of the intermediate layer.
6. The method of claim 1 , wherein removing the portions of the resist layer and the intermediate layer not masked by the first set of spacers comprises forming substantially vertical portions of the intermediate layer and the first set of spacers.
7. The method of claim 6 , wherein forming the substantially vertical portions of the intermediate layer and the first set of spacers comprises forming the substantially vertical portions of the intermediate layer and the first set of spacers having a thickness about equal to the second thickness of the first set of spacers.
8. The method of claim 1 , wherein forming the second spacers on the sidewalls of the remaining portions of the intermediate layer comprises forming the second spacers at a thickness about equal to the second thickness of the first set of spacers.
9. The method of claim 1 , wherein forming the openings in the resist layer located above the intermediate layer comprises forming the openings to have a third thickness of about three times the second thickness of the first set of spacers.