Metal Gate Work Function Tuning via Etch Stop Removal
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Solution Overview
Problem
The conventional gate last process for semiconductor devices with metal gates is complex and requires multiple layers, including an etch stop layer, which complicates the manufacturing process and affects the reliability of the gate trench filling.
Innovation Solution
A manufacturing method that omits the etch stop layer by forming a first and second work function metal layer with the same metal material in the gate trenches, followed by a gap-filling metal layer, ensuring the required work function is achieved without the need for an etch stop layer, thereby simplifying the process and improving gap-filling results.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the conventional gate last process is used with multiple layers including etch stop layer, then the work function requirements for different conductivity types can be met, but the process complexity increases and the reliability of gate trench filling deteriorates
Solution Approach 1:
The patent removes the etch stop layer from the conventional gate last process, extracting this unnecessary component to simplify the structure. By forming only the first and second work function metal layers directly in the gate trench without an etch stop layer, the process complexity is reduced while maintaining the ability to meet different work function requirements for P-type and N-type devices.
Solution Approach 2:
The patent combines the functions of multiple layers into a simplified structure. The first work function metal layer serves dual purposes: providing work function for P-type devices and acting as a barrier layer that prevents diffusion into N-type regions. This merging of functions eliminates the need for separate etch stop layer and reduces the total number of layers required.
2Manufacturing precision
If the etch stop layer is included in the gate trench structure, then the manufacturing process can proceed with conventional steps, but the gap-filling result deteriorates and process complexity increases
Solution Approach 1:
The etch stop layer is extracted/removed from the gate trench structure. This eliminates the interface discontinuities that cause poor gap-filling results. With only the work function metal layers remaining, the gap-filling process achieves better uniformity and precision without the complications introduced by multiple layer interfaces.
3Adaptability or versatility
If multiple work function metal layers with different materials are formed, then the work function requirements for P-type and N-type devices can be satisfied, but the process complexity increases
Solution Approach 1:
The patent applies local quality by forming the first work function metal layer with different thicknesses in different regions. The layer is formed thicker in P-type device regions to provide the required work function, while being thinner or selectively removed in N-type device regions. This spatial variation in layer quality allows different work function requirements to be met without requiring completely different material stacks.
Solution Approach 2:
The patent changes the thickness parameter of the first work function metal layer to achieve different effective work functions. By controlling the thickness of this layer, the work function can be adjusted to satisfy both P-type and N-type device requirements using the same base material, thereby reducing process complexity while maintaining adaptability.
Data Source
AI summary
A manufacturing method of semiconductor devices having metal gate includes following steps. A substrate having a first semiconductor device and a second semiconductor device formed thereon is provided. The first semiconductor device includes a first gate trench and the second semiconductor device includes a second gate trench. A first work function metal layer is formed in the first gate trench and the second gate trench. A portion of the first work function metal layer is removed from the second gate trench. A second work function metal layer is formed in the first gate trench and the second gate trench. The second work function metal layer and the first work function metal layer include the same metal material. A third work function metal layer and a gap-filling metal layer are sequentially formed in the first gate trench and the second gate trench.