Sacrificial Nitride Layer for Metal Gate CMP Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The 'gate last' process in semiconductor manufacturing, particularly with tungsten gate electrodes, faces issues like dishing during chemical mechanical polishing (CMP), leading to inadequate tungsten thickness and residual slurry particles adsorbing on the oxide dielectric layer, which are difficult to remove.
Innovation Solution
The introduction of a sacrificial nitride layer on the inter-layer dielectric layer with a concave top surface, allowing for controlled CMP and reducing dishing, and utilizing a tungsten layer with a CMP process that exposes the sacrificial nitride layer, thereby minimizing slurry particle adsorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If tungsten CMP process is performed to remove excess tungsten, then gate electrode thickness is controlled, but dishing occurs on the oxide dielectric layer surface
Solution Approach 1:
A sacrificial nitride layer is deposited on the oxide dielectric layer before the tungsten CMP process. This preliminary action creates a protective interface that prevents direct contact between the CMP slurry and the oxide dielectric layer, thereby preventing dishing while still allowing effective tungsten thickness control.
Solution Approach 2:
The sacrificial nitride layer acts as an intermediary between the CMP slurry and the oxide dielectric layer. During tungsten CMP, the nitride layer absorbs the mechanical and chemical effects that would otherwise cause dishing on the oxide surface, protecting it while enabling precise tungsten thickness control.
2Manufacturing precision
If tungsten CMP process is performed to control gate thickness, then resistivity is reduced, but residual slurry particles adsorb on the oxide dielectric layer
Solution Approach 1:
The sacrificial nitride layer serves as a mediator that prevents slurry particles from adsorbing onto the oxide dielectric layer. The nitride layer's surface properties are more resistant to slurry particle adhesion, and any particles that do adsorb can be easily removed without damaging the underlying oxide layer.
Solution Approach 2:
The sacrificial nitride layer is a temporary, disposable protective layer that is intentionally designed to be removed after serving its protective function during CMP. It absorbs the harmful effects of slurry particle adsorption, allowing the oxide dielectric layer to remain clean and free of difficult-to-remove particles.
3Ease of manufacture
If dummy polysilicon gates are removed to form gate trenches, then metal gate formation is enabled, but additional process steps are required
Solution Approach 1:
The removal of dummy polysilicon gates and the formation of gate trenches are combined with the subsequent metal layer deposition and CMP processes. The sacrificial nitride layer remains in place throughout these operations, allowing multiple steps to be performed without additional protective measures, thereby reducing overall process complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method effectively alleviates dishing and reduces slurry particle adsorption, ensuring adequate tungsten thickness and improved surface quality by controlling gate height and preventing particle accumulation.
Implementation Method 1
A first nitride layer is deposited on the first dummy gate, the second dummy gate, and the ILD layer
Implementation Method 2
The first nitride layer, the first nitride cap layer and the second nitride cap layer are polished, thereby exposing the first polysilicon layer and the second polysilicon layer
Implementation Method 3
A metal layer is deposited on the sacrificial nitride layer and within the first gate trench and the second gate trench
Data Source
AI summary
The present invention discloses a metal gate process. A sacrificial nitride layer is introduced during the fabrication of metal gates. The gate height can be well controlled by introducing the sacrificial nitride layer. Further, the particle fall-on problem can be effectively solved.