FET Gate Insulating Layer Protection via Selective Etching
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Solution Overview
Problem
Field effect transistors (FETs) face issues with etching damage to the gate insulating layer during the electrode etching process, leading to leakage current and adverse effects on electric characteristics.
Innovation Solution
A method for manufacturing FETs with a gate insulating layer made of an oxide film containing alkaline earth metals and elements like Ga, Sc, or lanthanides, where a first conductive film dissolves in an organic alkaline solution and a second conductive film is etched at a higher rate, using the second film as a mask to protect the gate insulating layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional etching process is used to pattern the conductive film on the gate insulating layer, then the electrode can be formed, but etching damage occurs to the gate insulating layer causing film thinning and leakage current
Solution Approach 1:
The patent introduces an intermediary protective film between the gate insulating layer and the etching process. This protective film serves as a buffer that absorbs the etching damage, preventing direct contact between the etching solution and the gate insulating layer. The protective film is specifically designed to be etched by the etching solution while protecting the underlying gate insulating layer from film thinning and leakage current issues.
Solution Approach 2:
The patent applies preliminary protective measures by forming the protective film on the gate insulating layer before the etching process begins. This preliminary action ensures that the gate insulating layer is pre-protected against etching damage, allowing the subsequent etching process to proceed without causing film thinning or leakage current in the gate insulating layer.
2Speed
If the gate insulating layer is made thinner to reduce capacitance, then switching speed improves, but leakage current increases and insulating properties deteriorate
Solution Approach 1:
The patent segments the insulating structure into multiple layers: the gate insulating layer and an additional protective film. This segmentation allows the gate insulating layer to be optimized for electrical performance (maintaining appropriate thickness for low leakage current) while the protective film provides additional insulation and protection, effectively decoupling the thickness constraint from the insulating property requirement.
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
Prevents etching damage to the gate insulating layer, maintaining good insulating properties and improving the electric characteristics of the FETs.
Implementation Method 1
a first conductive film that dissolves in an organic alkaline solution
Implementation Method 2
etching the second conductive film with an etching solution having a higher etch rate for the second conducive film as compared with an etch rate for the first conductive film
Data Source
AI summary
A method is provided for manufacturing a field effect transistor that includes a gate insulating layer and an electrode including a first conductive film and a second conductive film successively laminated on a predetermined surface of the gate insulating layer. The method includes forming an oxide film including element A, which is an alkaline earth metal, and element B, which is at least one of Ga, Sc, Y and a lanthanide, as the gate insulating layer; forming a first conductive film that dissolves in an organic alkaline solution on the oxide film; forming a second conductive film on the first conductive film; etching the second conductive film with an etching solution having a higher etch rate for the second conductive film as compared with that for the first conductive film; and etching the first conductive film with the organic alkaline solution using the second conductive film as a mask.