Split-Gate Memory Insulating Film Trench for Metal Diffusion
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Solution Overview
Problem
In the manufacturing of semiconductor devices with split-gate type flash memory, the use of high dielectric constant insulating films containing metals like hafnium can lead to metal diffusion during polishing, affecting the threshold of MISFETs and increasing junction leakage current, thereby reducing electrical reliability.
Innovation Solution
A method is introduced where a trench is formed between the control gate and memory gate electrodes with an insulating film different from the charge accumulation film, and this trench is filled with an insulating film to prevent metal diffusion during polishing, ensuring the electrical properties of MISFETs are maintained.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If CMP polishing is performed to expose control gate and memory gate electrodes, then the upper surfaces of the electrodes are exposed for subsequent processing, but metal in the charge accumulation film diffuses and adheres to the semiconductor substrate
Solution Approach 1:
An insulating film is introduced as an intermediary layer between the charge accumulation film containing metal and the semiconductor substrate. This insulating film prevents direct contact and diffusion paths, allowing CMP polishing to expose gate electrodes while blocking metal diffusion to the substrate, thereby resolving the contradiction between ease of operation and electrical reliability
2Ease of manufacture
If ion implantation is performed with metal present on the surface, then source and drain regions are formed, but metal diffuses into the semiconductor substrate increasing junction leakage current
Solution Approach 1:
The insulating film serves as a protective intermediary during ion implantation processes, allowing source and drain region formation while preventing metal contamination and diffusion into the semiconductor substrate, thus maintaining low junction leakage current
3Ease of manufacture
If metal diffuses into the gate insulating film of MISFET, then the threshold of MISFET varies, but this causes threshold variations that prevent desired electrical properties
Solution Approach 1:
The insulating film acts as a diffusion barrier that prevents metal atoms from reaching the gate insulating film of MISFET during polishing and subsequent processing, thereby maintaining precise threshold voltage control and desired electrical properties
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 reliability of semiconductor devices by preventing metal diffusion and maintaining desired electrical properties, thus reducing threshold variations and junction leakage currents.
Implementation Method 1
embedding the inside of the trench with an insulating film different from the charge accumulation film
Implementation Method 2
polishing so as to expose an upper surface of the control gate electrode and the memory gate electrode
Data Source
AI summary
A trench is formed by removing a portion of each of the charge accumulation film and the insulating film located between the control gate electrode and the memory gate electrode. The insulating film is formed in the trench so that the upper surface of each of the insulating film and the charge accumulation film is covered with the insulating film. When exposing the upper surface of the control gate electrode and the memory gate electrode, the upper surface of each of the insulating film and the charge accumulation film is not exposed.