Adhesion Layer Delamination Prevention in Nonvolatile Memory Contact Plugs
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Solution Overview
Problem
The conventional method for fabricating nonvolatile semiconductor memory devices using ferroelectric films faces issues with adhesion layer delamination from silicon nitride hydrogen barrier films, leading to reduced yield and degradation of barrier properties due to hydrogen diffusion and over-polishing during contact plug formation.
Innovation Solution
A method involving the formation of a multilayer film with a silicon nitride hydrogen barrier film and a silicon dioxide film, where the adhesion layer is formed on the silicon dioxide film, preventing delamination and over-polishing, and using CMP to remove conductive film portions over the silicon dioxide film, ensuring high selectivity and maintaining hydrogen barrier integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the adhesion layer is formed on the silicon nitride hydrogen barrier film, then the contact plug can be formed, but the adhesion layer delaminates from the silicon nitride film
Solution Approach 1:
A silicon dioxide film is introduced as an intermediary layer between the silicon nitride hydrogen barrier film and the adhesion layer. This intermediary silicon dioxide film prevents direct contact between the adhesion layer and silicon nitride, eliminating the delamination problem while still allowing the contact plug to be formed effectively.
2Ease of manufacture
If CMP is used to remove contact plug material and adhesion layer, then the contact plug can be formed, but the hydrogen barrier film is over-polished and scratched
Solution Approach 1:
The silicon dioxide film is deposited beforehand as a cushioning protective layer over the silicon nitride hydrogen barrier film. During the CMP process, this silicon dioxide film absorbs the polishing action, preventing the polishing pads from directly contacting and damaging the silicon nitride film. The silicon dioxide film can be removed later without affecting the underlying hydrogen barrier film.
3Object-generated harmful factors
If the adhesion layer delaminates, then particles are generated in the CVD system, but this reduces product yield
Solution Approach 1:
The silicon dioxide film serves as a stable intermediary layer that prevents adhesion layer delamination. By eliminating the delamination issue, the source of particles in the CVD system is removed, thereby improving product yield without sacrificing manufacturing capability.
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 enhances the yield and reliability of nonvolatile semiconductor memory devices by preventing adhesion layer delamination and maintaining the hydrogen barrier property, improving surface planarity and reducing hydrogen diffusion effects.
Implementation Method 1
a silicon nitride film as a hydrogen barrier film
Implementation Method 2
removing respective portions of the conductive film and the silicon dioxide film which are located over the silicon nitride film by CMP
Data Source
AI summary
An adhesion layer composed of a titanium film and a titanium nitride film is formed by CVD on the inner wall of a contact hole formed in a multilayer film composed of an interlayer insulating film, a silicon nitride film, and a silicon dioxide film. Then, a conductive film made of tungsten or polysilicon is filled by CVD in the contact hole and the respective portions of the conductive film and the adhesion layer which are located over the silicon dioxide film are removed by CMP. Subsequently, the silicon dioxide film is removed by an etch-back method or a CMP method so that the silicon nitride film is exposed. This can prevent the delamination of the adhesion layer from the silicon nitride film as a hydrogen barrier film and also prevent the formation of a scratch in the silicon nitride film.