MIS Capacitor Conductive Side Layer for High Frequency
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Solution Overview
Problem
Conventional MIS capacitors with semiconductor substrates exhibit low electrical conductivity, leading to restricted usage in high frequency ranges due to low quality factors, particularly below 3 GHz, as most of the resistance occurs within the conductive silicon substrate, limiting their performance in high-frequency applications.
Innovation Solution
The implementation of a conductive layer with higher electrical conductivity on the side surfaces of the lower electrode and potentially on the upper surface areas not covered by the insulating layer, allowing electrical signals to pass through the conductive layer instead of the low conductivity substrate, thereby reducing energy loss and enhancing the quality factor, especially in high frequency areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a semiconductor substrate is used as the lower electrode, then the capacitor can be manufactured using semiconductor processes, but the electrical conductivity is low leading to low quality factors
Solution Approach 1:
The lower electrode is constructed as a composite structure combining a semiconductor substrate (providing manufacturability) with a conductive layer (providing high electrical conductivity). This composite approach allows the capacitor to benefit from both the ease of semiconductor manufacturing and the high conductivity needed for high quality factors.
Solution Approach 2:
A conductive layer is selectively formed on specific regions of the semiconductor substrate, particularly on the front surface and side surfaces where electrical signal transmission occurs. This local enhancement of conductivity addresses the specific problem areas without requiring the entire substrate to be replaced.
2Reliability
If the lower electrode is made of conductive silicon substrate, then electrical conductivity is improved, but resistance still occurs within the substrate limiting high frequency performance
Solution Approach 1:
The conductive layer is selectively applied to regions where electrical signals are transmitted (front surface and side surfaces), creating low-resistance pathways exactly where needed. This localized approach minimizes energy loss in critical signal paths while maintaining the benefits of the semiconductor substrate.
Solution Approach 2:
The conductive layer acts as an intermediary between the external circuit and the semiconductor substrate, providing a low-resistance interface that reduces the impact of substrate resistance. This intermediary layer allows signals to bypass the higher-resistance substrate regions.
3Reliability
If a conductive layer is added to improve conductivity, then quality factor increases, but device complexity increases
Solution Approach 1:
The conductive layer is implemented as a thin film deposited on the semiconductor substrate, adding minimal structural complexity while providing the necessary conductivity enhancement. This thin-film approach is compatible with standard semiconductor manufacturing processes.
Solution Approach 2:
The conductivity parameter of the lower electrode is improved by adding the conductive layer, achieving higher quality factors. While this does increase structural complexity, the change is minimal and can be integrated into existing manufacturing flows.
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 configuration improves the quality factor of MIS capacitors by reducing energy loss and enabling effective signal transmission at higher frequencies, extending their usable range beyond 3 GHz by compensating for the low conductivity of the semiconductor substrate.
Implementation Method 1
a first conductive layer formed on side surfaces of the lower electrode so that the electrical signal passing a lower surface and an upper surface of the lower electrode passes along the side surfaces of the lower electrode
Data Source
AI summary
In one embodiment of the present invention, there is provided an MIS capacitor, including: a lower electrode formed with a semiconductor substrate having electrical conductivity and through which an electrical signal passes at a lower surface thereof; an insulating layer formed on the lower electrode; an upper electrode formed on the insulating layer and through which the electrical signal passes at an upper surface thereof; and a first conductive layer formed on side surfaces of the lower electrode so that the electrical signal passing the lower surface and an upper surface of the lower electrode passes along the side surfaces of the lower electrode, wherein the first conductive layer has electro conductivity higher than the electro conductivity of the lower electrode.