Metal Gate Fabrication via Ashable Mandrel for ILD0 Loss Control
Solution Overview
Problem
The conventional two-step CMP process for manufacturing semiconductor devices with aluminum gate structures faces challenges in filling gate materials due to increased ILD0 losses, which deepen the cavity and complicate the filling process.
Innovation Solution
A method is introduced where a thin ashable film layer and a second dielectric layer are formed over the ILD0 layer, allowing for reduced ILD0 loss during aluminum CMP by removing these layers through polishing and ashing, thereby reducing the initial height of the cavity and improving gate material filling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional two-step CMP process is used for aluminum gate structures, then the gate electrode can be formed, but ILD0 losses increase and the cavity deepens, complicating the filling process
Solution Approach 1:
A mandrel layer is formed over the ILD0 layer before the aluminum CMP process. This mandrel layer serves as a protective structure that prevents excessive removal of the ILD0 layer during CMP, thereby maintaining cavity depth within acceptable limits and facilitating subsequent gate material filling operations
Solution Approach 2:
The mandrel layer acts as an intermediary protective layer between the ILD0 layer and the CMP polishing head. It mediates the mechanical removal process by being selectively removed after serving its protective function, thereby preventing direct excessive contact between the CMP process and the ILD0 layer
2Loss of substance
If the ILD0 layer is excessively removed during CMP, then the cavity deepens, but this increases the complexity and difficulty of filling gate materials
Solution Approach 1:
The mandrel layer is formed in advance over the ILD0 layer to establish a protective barrier before the CMP process begins. This preliminary structure prevents uncontrolled removal of ILD0 material during polishing, maintaining the cavity at an appropriate depth for subsequent filling operations
Solution Approach 2:
The mandrel layer provides a cushioning effect during the CMP process, absorbing the mechanical removal action that would otherwise directly affect the ILD0 layer. This cushioning protects the ILD0 layer from excessive removal and maintains suitable cavity dimensions for gate material filling
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 approach reduces ILD0 loss and initial dummy gate height, simplifying the filling process and enhancing the accuracy of metal gate formation in semiconductor devices.
Implementation Method 1
removing first ashable film layer through an ashing method
Data Source
AI summary
One aspect of the present disclosure is a method of fabricating metal gate by forming special layers in place of traditional TiN hard mask over the ILD0 layer to avoid ILD0 losses due to conventional ILD0 CMP. The method can comprise: after the ILD0 CMP, forming a first thin ashable film layer over the ILD0 layer; then forming a second thin dielectric layer over the first layer; during the aluminum CMP process for a first region (PMOS or NMOS), removing the second layer through polishing until the top surface of the first ashable film layer; and then removing first ashable film layer through an ashing method such as burning. In this way, ILD0 loss can be reduced during the first aluminum CMP step and thus can reduce initial height of ILD0, which in turn can reduce the height of initial dummy gate filled in the cavity.