Recessed Gate Electrode Void Migration Prevention
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Solution Overview
Problem
Voids in recessed gate electrodes of semiconductor devices can migrate, leading to leakage current and fluctuating threshold voltage, deteriorating the electrical characteristics of MOS transistors due to silicon diffusion during subsequent processes.
Innovation Solution
A recessed gate electrode structure is designed with a first and second recess, where the second recess is larger and doped with impurities at a higher density to prevent void migration, using polysilicon layers with specific impurity densities to inhibit silicon diffusion and maintain electrical integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the recess is filled with conductive material to form a gate electrode, then the gate electrode occupies minimal area on the substrate, but voids are formed within the conductive material due to clogging of the upper portion
Solution Approach 1:
The patent changes the geometric parameters of the recess by forming a first recess and a second recess with different maximum diameters, where the second recess has a larger maximum diameter than the first recess. This parameter change prevents clogging of the upper portion during filling, eliminating void formation while maintaining minimal area occupation.
2Productivity
If subsequent processes are performed to complete device fabrication, then device integration is achieved, but voids migrate due to silicon diffusion causing leakage current and threshold voltage fluctuation
Solution Approach 1:
The patent applies preliminary anti-action by forming a specific multi-layer recess structure before filling with conductive material. This pre-formed structure with varying maximum diameters prevents void formation at the source, thereby preventing subsequent void migration and its harmful effects during later fabrication processes.
3Ease of manufacture
If the recess has a larger maximum diameter in the lower portion to facilitate filling, then filling is easier, but voids are formed in the central region of the conductive material
Solution Approach 1:
The patent segments the recess into multiple distinct regions: a first recess with a first maximum diameter and a second recess with a second maximum diameter. This segmentation allows each region to serve a specific function - the larger second recess facilitates filling while the structured transition prevents void formation in the conductive material.
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
The solution effectively minimizes void migration, reducing leakage current and threshold voltage fluctuations, thereby enhancing the operational characteristics of MOS transistors by preventing impurity diffusion and maintaining electrical stability.
Implementation Method 1
voids of recessed gate electrodes can migrate easily due to silicon diffusion facilitated during subsequent processes
Implementation Method 2
a gate oxide layer 12 is formed over the top surface of the substrate 10 and along inner surfaces of a recess formed in the substrate 10
Data Source
AI summary
A recessed gate electrode structure includes a first recess and a second recess in communication with the first recess both formed in a substrate. The second recess is larger than the first recess. A gate dielectric layer is formed on a top surface of the substrate and on an inner surface of the first and second recesses. A first polysilicon layer fills the first recess and is doped with impurities at a first impurity density. A second polysilicon layer fills the second recess and is doped with the impurities at a second impurity density. A void is defined within the second polysilicon layer. A third polysilicon layer is formed on the gate dielectric and first polysilicon layers and is doped with the impurities at a third impurity density. Due to impurities in the second polysilicon layer, migration of the void within the second recess may be substantially prevented.