SOI and Bulk Region Integration for Leakage and Floating Body Control
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Solution Overview
Problem
Semiconductor-on-insulator technology faces challenges such as the floating body effect, which limits its suitability for certain applications, and fully depleted field effect transistors may not be ideal for all use cases, particularly in digital and analog integrated circuits.
Innovation Solution
A structure and method that combine a semiconductor-on-insulator region with a bulk region on the same semiconductor substrate, allowing for the formation of field effect transistors with both semiconductor-on-insulator and bulk configurations, enabling the integration of high-performance devices and high-voltage devices on the same chip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If semiconductor-on-insulator technology is used, then parasitic capacitances and leakage currents are reduced, but floating body effect occurs causing threshold voltage dependence on previous states
Solution Approach 1:
The substrate is divided into two distinct regions: a first region with semiconductor-on-insulator structure and a second region with bulk semiconductor structure. This segmentation allows each region to be optimized for different functions - the SOI region for low leakage and the bulk region for avoiding floating body effects, thereby resolving the contradiction between reducing parasitic effects and eliminating floating body issues.
Solution Approach 2:
Different semiconductor structures are applied to different locations on the substrate. The first region uses thin-film semiconductor-on-insulator for applications requiring low parasitic capacitance and leakage, while the second region uses bulk semiconductor for applications requiring stable threshold voltage independent of previous states. This local differentiation resolves the contradiction by providing appropriate characteristics in each location.
2Object-generated harmful factors
If fully depleted field effect transistors are used to avoid floating body effect, then device characteristics are improved, but suitability for digital and analog integrated circuits is reduced
Solution Approach 1:
The substrate is segmented into regions supporting different transistor types. Fully depleted transistors are placed in the first region where their low leakage characteristics are beneficial, while conventional bulk transistors are placed in the second region where they provide better digital and analog circuit performance. This segmentation allows the system to achieve both floating body effect avoidance and broad circuit applicability.
Solution Approach 2:
The semiconductor substrate is designed to support multiple types of field effect transistors (both fully depleted and conventional bulk types) on the same chip. This multi-functionality enables the integrated circuit to incorporate devices optimized for different applications - fully depleted transistors for low-power applications and bulk transistors for digital and analog circuits - thereby achieving both floating body effect mitigation and broad adaptability.
3Adaptability or versatility
If field effect transistors are formed on bulk substrate, then device characteristics are suitable for digital and analog circuits, but parasitic capacitances and leakage currents increase
Solution Approach 1:
The substrate is divided into two regions with different semiconductor structures. The first region uses semiconductor-on-insulator to minimize parasitic capacitances and leakage currents, while the second region uses bulk semiconductor to provide suitable device characteristics for digital and analog circuits. This spatial segmentation allows both contradictory requirements to be satisfied in different locations.
Solution Approach 2:
Different semiconductor structures are applied locally to different regions based on circuit requirements. Regions requiring low parasitic effects use SOI structure, while regions requiring robust digital and analog performance use bulk structure. This local optimization resolves the contradiction by matching structure to function in each location.
Data Source
AI summary
A structure comprises a semiconductor substrate, a semiconductor-on-insulator region and a bulk region. The semiconductor-on-insulator region comprises a first semiconductor region, a dielectric layer provided between the semiconductor substrate and the first semiconductor region, and a first transistor comprising an active region provided in the first semiconductor region. The dielectric layer provides electrical isolation between the first semiconductor region and the semiconductor substrate. The bulk region comprises a second semiconductor region provided directly on the semiconductor substrate.