Gate Insulating Film Thickness Control via Selective Oxidation
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Solution Overview
Problem
In semiconductor device manufacturing, reduced thicknesses of gate insulating films can cause size variations among gate electrodes and decrease reliability, due to differences in etching rates influenced by ion implantation conditions for well and channel ion implantations, leading to potential overetching or insufficient removal of silicon dioxide films.
Innovation Solution
A method involving sequential oxidation and etching steps to form gate insulating films of varying thicknesses, where silicon dioxide films are selectively removed and re-formed to achieve precise thicknesses for different transistor types, minimizing etching variations and ensuring uniformity across the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single gate insulating film thickness is used across all transistor areas, then the manufacturing process is simple, but transistors with different driving voltages cannot be achieved
Solution Approach 1:
The patent applies local quality by forming gate insulating films with different thicknesses in different transistor areas. Specifically, a first gate insulating film with a first thickness is formed in a first transistor area, while a second gate insulating film with a second thickness (different from the first) is formed in a second transistor area. This allows transistors in different areas to have different driving voltages tailored to their specific requirements, while maintaining a unified manufacturing process approach.
2Adaptability or versatility
If gate insulating films of different thicknesses are formed using conventional methods, then transistors with different driving voltages can be achieved, but size variations among gate electrodes and reliability decrease occur
Solution Approach 1:
The patent applies preliminary action by performing selective removal of portions of the gate insulating film before final gate electrode formation. Specifically, portions of the gate insulating film are selectively removed in certain transistor areas to adjust the effective thickness, and this is done before forming the gate electrodes. This preliminary adjustment ensures uniform gate electrode dimensions and prevents size variations, while maintaining the different thickness requirements for different driving voltages.
Solution Approach 2:
The patent applies segmentation by dividing the gate insulating film formation into multiple controlled steps. Different portions of the gate insulating film are selectively treated (removed or retained) in different transistor areas through separate processing steps. This segmented approach allows precise control over the final gate insulating film thickness in each area, ensuring both the different thickness requirements for various driving voltages and the uniformity of gate electrode dimensions.
3Reliability
If ion implantation is performed for well and channel formation, then transistor characteristics are adjusted, but etching rate variations occur leading to overetching or insufficient removal of silicon dioxide films
Solution Approach 1:
The patent applies parameter changes by adjusting the thickness of the gate insulating film rather than relying solely on etching parameters. By controlling the oxidation conditions and film formation parameters, the patent achieves the desired gate insulating film thicknesses in different areas without being constrained by the etching rate variations caused by ion implantation. This shifts the control parameter from etching depth to film formation thickness, thereby maintaining manufacturing precision despite ion implantation effects.
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 size variations among gate electrodes, prevents electric field concentration, and enhances the reliability and yield of semiconductor devices by maintaining consistent film thicknesses and reducing the risk of overetching or underetching during manufacturing.
Implementation Method 1
oxidizing a surface of a semiconductor substrate to form a first insulating film covering a first area, a second area, and a third area of the semiconductor substrate
Data Source
AI summary
A method of manufacturing a semiconductor device includes oxidizing a surface of a semiconductor substrate to form a first insulating film covering a first area, a second area, and a third area of the semiconductor substrate; removing the portions of the first insulating film lying on the first area and the second area; oxidizing the surface of the semiconductor substrate to form a second insulating film covering the first area and the second area and further oxidizing the third area covered with the first insulating film; and removing the portion of the second insulating film lying on from the second area and the portion of the first insulating film lying on the third area.