BACKGROUND

The semiconductor integrated circuit (IC) industry has experienced exponential growth. Technological advances in IC materials and design have produced generations of ICs where each generation has smaller and more complex circuits than the previous generation. In the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased. This scaling down process generally provides benefits by increasing production efficiency and lowering associated costs. Such scaling down has also increased the complexity of processing and manufacturing ICs.

For example, when forming n-type and p-type epitaxial source/drain (S/D) features for small-scaled transistors, such as field effect transistors (FET) having fin-like channel (so-called “FinFETs”), sometimes fins in S/D regions are first recessed. Resist (or photoresist) material is patterned to expose regions for one type of FinFETs (e.g., p-type FinFETs) while covering other regions for another type of FinFETS (e.g., n-type FinFETs). However, there are challenges to implementing such IC fabrication processes, especially with scaled down IC features in advanced process nodes. For example, as the scaling down continues, distance between adjacent gate structures over fins decreases. Accompanying the decreasing in gate distance, it becomes difficult during resist material patterning to remove resist material stacked between gate structures, resulting in remaining resist residue. Particularly, along boundary line between different regions for n-type FinFETs and p-type FinFETs, resist material may form curvy sidewalls. The curvy sidewalls may extend into the regions supposed to be exposed and cover fins near the boundary line, which may cause fin height uniformity issue after fin recess and thus deteriorate device performance. An object of the present disclosure seeks to resolve this issue, among others.

