SOI Transistor Heat Dissipation via Peltier Effect
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Solution Overview
Problem
SOI field effect transistors with Schottky source/drain face significant self-heating issues due to poor heat dissipation, hindered by the thick silicon oxide layer and thin silicon film, which affects electrical performance and reliability.
Innovation Solution
A heat dissipation structure with holes filled with N-type and P-type materials of high thermoelectric coefficient, connected via ohmic contacts and metal wires, utilizing the Peltier effect to absorb and dissipate heat directly from the source and drain terminals to the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick silicon oxide layer is used as the buried oxide layer, then the device achieves effective suppression of short channel effect and excellent subthreshold swing, but the thermal conductivity decreases significantly, hindering heat dissipation from the channel to the substrate
Solution Approach 1:
The patent introduces a heat dissipation layer comprising thermally conductive material (such as diamond, cubic boron nitride, or graphene) as an intermediary between the silicon channel and the silicon oxide substrate. This intermediary layer has high thermal conductivity (≥100 W/m/K) that bridges the thermal gap created by the thick silicon oxide buried layer, enabling efficient heat transfer from the channel to the substrate while maintaining the electrical isolation benefits of the SOI structure
Solution Approach 2:
The patent creates a composite structure by combining the silicon channel, the thermally conductive heat dissipation layer, and the silicon oxide buried layer. This composite material approach allows the system to simultaneously achieve the electrical properties of SOI devices (short channel effect suppression) and the thermal properties of high-conductivity materials (effective heat dissipation), resolving the contradiction between electrical performance and thermal management
2Reliability
If a very thin silicon film is used for the channel, then the device achieves reduced series resistance and improved device performance, but the thermal conductivity of the silicon film decreases due to surface phonon scattering, further suppressing heat dissipation
Solution Approach 1:
The thermally conductive heat dissipation layer serves as a mediator between the thin silicon channel and the substrate. Since the thin silicon film itself has reduced thermal conductivity due to surface phonon scattering, the heat dissipation layer with high thermal conductivity (≥100 W/m/K) provides an alternative efficient thermal pathway, extracting heat from the channel region without requiring the silicon film itself to have high thermal conductivity
Solution Approach 2:
The patent applies local quality by introducing the thermally conductive material specifically in the region where heat dissipation is most critical (under the channel and source/drain regions), while maintaining the thin silicon film structure elsewhere for optimal electrical performance. This localized approach allows the thin silicon film to maintain its electrical advantages while the heat dissipation layer compensates for its thermal deficiencies
3Temperature
If a heat dissipating layer with high thermal conductivity (such as graphene) is added onto the buried oxide layer, then lateral heat dissipation is improved, but the heat dissipation structure is not connected to the device directly, resulting in poor dissipation effect
Solution Approach 1:
The heat dissipation layer acts as a thermal intermediary that is directly coupled to the channel and source/drain regions through thermal contact. Unlike previous approaches where the heat dissipation layer was merely placed on the buried oxide, this intermediary layer is positioned and configured to maintain direct thermal interaction with the active device regions, ensuring efficient heat transfer from the heat generation sites to the heat dissipation pathways
Solution Approach 2:
The patent transitions from purely lateral heat dissipation (in the plane of the device) to include vertical heat dissipation pathways. The thermally conductive layer provides a vertical thermal conduction path from the channel through the heat dissipation layer to the substrate, adding a third dimension to heat dissipation and significantly improving overall heat removal efficiency beyond what lateral dissipation alone can achieve
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 solution effectively reduces the temperature of the source and drain terminals, improving device performance by directly connecting the heat dissipation structure to the active regions and allowing for controlled operation, compatible with CMOS processes and applicable to various SOI field effect transistors.
Implementation Method 1
By way of the Peltier effect, in the present invention heat can be absorbed at the contact portions between the thermoelectric materials and the source/drain, and be dissipated at the connection portions between the thermoelectric materials and bottom electrode metals
Data Source
AI summary
The present invention discloses a heat dissipation structure for a SOI field effect transistor having a schottky source/drain, which relates to a field of microelectronics. The heat dissipation structure includes two holes connected with a drain terminal or with both a source terminal and a drain terminal, which are filled with an N-type material with high thermoelectric coefficient and a P-type material with high thermoelectric coefficient respectively. A metal wire for the N-type material with high thermoelectric coefficient in the vicinity of the drain terminal is applied a high potential with respect to the drain terminal, and a metal wire for the P-type material with high thermoelectric coefficient in the vicinity of the drain terminal is applied a low potential with respect to the drain terminal. A metal wire for the N-type material with high thermoelectric coefficient in the vicinity of the source terminal is applied a high potential with respect to the source terminal, and a metal wire for the P-type material in the vicinity of the source terminal is applied a lower potential with respect to the source terminal. By way of a Peltier effect, in the present invention heat can be absorbed at a contact portion between the thermoelectric material and the source/drain, and at the same time dissipated at a connection portion between the thermoelectric material and a bottom electrode metal, so that the heat generated in an active region of the device is effectively transferred to the substrate and dissipated through a heat sink.