Method for mitigating layout effect in FINFET
Multigate devices and fabrication methods that mitigate the layout effects are described. In conventional processes to fabricate multigate semiconductor devices such as FinFET devices, long isolation cut masks may be used. This can lead to undesirable layout effects. To mitigate or eliminate the layout effect, fabrication methods are proposed in which the interlayer dielectric (ILD) layer remains intact at the gate cut location during the fabrication process.
1. A method for forming a semiconductor device, the method comprising:
forming a shallow trench isolation (STI) layer on a substrate;
forming first and second dummy gates on the STI layer;
forming an interlayer dielectric (ILD) layer on the STI layer, the ILD layer corresponding to a gate cut region and separating the first and second dummy gates;
forming a first mask on the first and second dummy gates and on the ILD layer, the first mask having a trench corresponding to an isolation cut region and exposing the first and second dummy gates and the ILD layer, the isolation cut region being a region of an isolation cut mask, and the gate cut region intersecting the isolation cut region;
forming a second mask on the first mask and on the ILD layer exposed by the trench;
removing the first and second dummy gates;
removing the first and second masks such that the ILD layer remains on the STI layer; and
filling regions left by the removed first and second dummy gates.
2. The method of claim 1 , wherein the gate cut and the isolation cut regions are substantially perpendicular to each other.
3. The method of claim 1 , wherein the first and second masks have different etch selectivities.
4. The method of claim 1 , wherein forming the first mask comprises:
depositing the first mask on the first and second dummy gates and on the ILD layer;
depositing a first photoresist on the first mask, the first photoresist having an opening corresponding to the isolation cut region, and the opening exposing a portion of the first mask;
etching the exposed portion of the first mask to form the trench; and
removing the first photoresist.
5. The method of claim 1 , wherein removing the first and second dummy gates comprises:
depositing a second photoresist on the second mask, the second photoresist corresponding to the gate cut region such that a portion of the second mask outside of the gate cut region is exposed;
removing the exposed portion of the second mask so as to expose the first and second dummy gates outside of the gate cut region;
removing the second photoresist; and
removing the first and second dummy gates such that the ILD layer corresponding to the gate cut region remains intact.
6. The method of claim 1 , wherein the first mask is a hardmask.
7. The method of claim 1 , wherein the second mask is a softmask.
8. The method of claim 1 , wherein filling the regions left by the removed first and second dummy gates comprises filling the regions with SiN and/or SiO.
9. A method for forming a semiconductor device, the method comprising:
forming a shallow trench isolation (STI) layer on a substrate;
forming first and second dummy gates on the STI layer;
forming an interlayer dielectric (ILD) layer on the STI layer, the ILD layer corresponding to a gate cut region and separating the first and second dummy gates;
forming a first mask on the first and second dummy gates and on the ILD layer;
forming a second mask on the first mask, the second mask corresponding to the gate cut region such that a portion of the first mask outside of the gate cut region is exposed;
removing the exposed portion of the first mask and the second mask such that a portion of the first mask corresponding to the gate cut region remains on the ILD layer;
removing the first and second dummy gates;
removing the first mask such that the ILD layer remains on the STI layer; and
filling regions left by the removed first and second dummy gates.
10. The method of claim 9 , wherein forming the second mask on the first mask comprises:
depositing the second mask on the first mask;
depositing a first photoresist over the second mask, the first photoresist corresponding to the gate cut region such that a portion of the second mask outside the gate cut region is exposed;
removing the exposed portion of the second mask so as to expose a portion of the first mask outside of the gate cut region; and
removing the first photoresist.
11. The method of claim 9 , wherein removing the exposed portion of the first mask and the second mask comprises:
depositing a second photoresist on the second mask, the second photoresist corresponding to the gate cut region and having an opening exposing a part of the second mask corresponding to an intersection between the gate cut region and an isolation cut region;
selectively removing the exposed portion of the first mask such that a portion of the first mask corresponding to the gate cut region below the second mask remains and the ILD layer below the first mask also remains; and
removing the second photoresist; and
removing the second mask such that the first mask corresponding to the gate cut region is exposed.
12. The method of claim 11 , wherein the gate cut and the isolation cut regions are substantially perpendicular to each other.
13. The method of claim 9 , wherein the first and second masks have different etch selectivities.
14. The method of claim 9 , wherein the first mask is one of SiN and SiO 2 and the second mask is the other of the SiN and SiO 2 .
15. The method of claim 9 , wherein filling the regions left by the removed first and second dummy gates comprises filling the regions with SiN and/or SiO.