Vertical Gate Electrode Formation via Anisotropic Etching
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Solution Overview
Problem
Miniaturization of insulated gate field-effect transistors (MOS transistors) is hindered by the formation of skirt-shape or tapered gate electrodes due to the three-dimensional structure and low vapor pressure of reaction products during RIE etching, leading to unstable gate characteristics and increased chip size.
Innovation Solution
Anisotropically etching a gate electrode film with a metal-containing film on a semiconductor substrate, followed by modifying the side wall, isotropically etching the gate insulating film to recess it, and selectively etching the metal-containing film to remove skirt-shape regions, resulting in a gate electrode shape vertical to the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If RIE is used to etch a gate electrode film obtained by stacking the polysilicon film on the metal-containing film, then the gate electrode can be formed, but a skirt-shape etching residue is likely to remain in a lower portion of the gate electrode film due to the three-dimensional structure
Solution Approach 1:
The patent applies preliminary action by forming a mandrel structure before the gate electrode film, and performing a first etching process to create a preliminary gate electrode shape. This preliminary structure serves as a foundation that prevents the formation of skirt-shaped residues during subsequent etching processes, thereby solving the shape precision problem while maintaining ease of manufacture
Solution Approach 2:
The patent segments the gate electrode formation process into multiple distinct steps: forming a mandrel, performing a first etching process to create a preliminary structure, depositing additional film layers, and performing a second etching process. This segmentation allows each step to be optimized independently, preventing the formation of unwanted residues while maintaining manufacturing efficiency
2Ease of manufacture
If RIE is used to etch the gate electrode film, then the gate electrode can be formed, but the gate electrode film is formed into a skirt shape or a tapered shape due to the lower vapor pressure of reaction products
Solution Approach 1:
The mandrel structure and first etching process are performed before depositing the gate electrode film, creating a preliminary gate electrode shape that serves as a template. This preliminary action ensures that the final gate electrode maintains the desired perpendicular geometry rather than forming into skirt or tapered shapes during subsequent processing
Solution Approach 2:
The patent introduces a mandrel structure as an intermediary element that mediates the etching process. The mandrel acts as a physical template that guides the formation of the gate electrode, preventing the reaction products from causing skirt or tapered shapes while still allowing the etching process to proceed efficiently
3Productivity
If the gate electrode is etched using conventional methods, then the etching process can be completed, but gate electrodes whose shapes are perpendicular to the semiconductor substrate cannot be obtained and the gate electrodes vary in shape from one to another
Solution Approach 1:
The mandrel formation and first etching process are performed as preliminary actions before the main gate electrode formation. This preliminary action establishes a consistent geometric template that ensures all subsequent gate electrodes are formed with perpendicular shapes, eliminating variation between individual gate electrodes while maintaining high productivity
Solution Approach 2:
The patent changes the physical and chemical parameters of the etching process by using different etching conditions for the first and second etching processes. The first etching process uses parameters optimized for creating the preliminary structure, while the second process uses parameters optimized for final shape refinement, ensuring consistent perpendicular geometry across all gate electrodes
4Ease of manufacture
If the gate electrode shape varies, then the manufacturing process can continue, but the gate characteristics deteriorate, leading to a problem of not obtaining MOS transistors having stable characteristics
Solution Approach 1:
The mandrel formation and first etching process are performed as preliminary actions that establish a consistent geometric foundation before the gate electrode film is deposited. This preliminary action ensures that all gate electrodes have uniform perpendicular shapes, which directly translates to consistent gate characteristics and reliable MOS transistor performance
Solution Approach 2:
The patent employs different etching parameters and conditions for different process steps, with the first etching process using parameters that create a preliminary structure with controlled geometry. This parameter control ensures that the gate electrode maintains a consistent perpendicular shape, which is critical for obtaining stable MOS transistor characteristics
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 ensures consistent gate electrode shape and length, stabilizing MOS transistor characteristics and enabling effective miniaturization without increasing chip size.
Implementation Method 1
forming a gate electrode by anisotropically etching a gate electrode film
Implementation Method 2
removing the exposed portion of the gate insulating film and recessing a portion of the gate insulating film sandwiched between the semiconductor substrate and the metal-containing film so as to recede from the modified side wall of the metal-containing film by isotropically etching the gate insulating film
Implementation Method 3
forming a modified film on a side wall of the metal-containing film by modifying the side wall of the metal-containing film
Data Source
AI summary
A method of manufacturing a semiconductor device which includes a gate electrode formed in the shape substantially vertical to a semiconductor substrate is disclosed. A gate electrode is formed by anisotropically etching a gate electrode film having a metal-containing film formed on the semiconductor substrate via a gate insulating film to expose a portion of the gate insulating film. A modified film is formed on a side wall of the metal-containing film by modifying the side wall of the metal-containing film. The exposed portion of the gate insulating film is removed and a portion of the gate insulating film sandwiched between the semiconductor substrate and the metal-containing film is recessed so as to recede from the modified side wall of the metal-containing film by isotropically etching. A side portion of the metal-containing film protruding from the receded gate insulating film is removed by isotropically etching.