Integrated Circuit Bipolar Transistor Resistive Element Integration
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Solution Overview
Problem
The manufacturing process for integrated circuits with heterojunction bipolar transistors and resistive elements on high thermal conductivity substrates is lengthy due to the need for additional steps such as epitaxial growth and buffer layer formation, which compromises both crystalline quality and heat dissipation performance.
Innovation Solution
The process involves forming a resistive material layer and a metal layer on a substrate with high thermal conductivity, where the metal layer serves as both a sub-collector for the bipolar transistor and an interconnect for the resistive element, allowing for simultaneous patterning and integration, thereby reducing the number of manufacturing steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If epitaxial growth is performed on a heterogeneous substrate to achieve high crystalline quality, then crystalline quality is improved, but heat dissipation performance deteriorates due to the need for a thick buffer layer with lower thermal conductivity
Solution Approach 1:
The invention divides the device into two separate substrates: a first substrate for growing the heterojunction bipolar transistor with high crystalline quality, and a second substrate providing high thermal conductivity for heat dissipation. This segmentation allows each substrate to be optimized for its specific function without compromise.
Solution Approach 2:
The invention introduces an intermediary structure (the first substrate with high thermal conductivity) that couples the bipolar transistor to the second substrate. This intermediary enables efficient heat transfer from the transistor to the high thermal conductivity substrate while maintaining the crystalline quality of the transistor structure.
2Speed
If the operating current of a heterojunction bipolar transistor is increased to reduce charge and discharge time, then operation speed is improved, but temperature increases due to self-heating
Solution Approach 1:
The invention extracts the heat dissipation function from the transistor structure itself and assigns it to a dedicated second substrate with high thermal conductivity. This allows the transistor to operate at high currents for fast switching while the heat is rapidly conducted away through the separate substrate.
Solution Approach 2:
The first substrate acts as an intermediary that provides a low thermal resistance path between the bipolar transistor and the second substrate. This intermediary enables the transistor to dissipate heat efficiently during high-current operation, maintaining low temperature despite increased operating speed.
3Manufacturing precision
If additional manufacturing steps such as buffer layer formation are added to achieve high crystalline quality on heterogeneous substrates, then crystalline quality is improved, but manufacturing process length increases
Solution Approach 1:
The invention segments the manufacturing process into two independent parts: growing the bipolar transistor on a lattice-matched substrate (avoiding buffer layers), and separately preparing a high thermal conductivity substrate. This eliminates the need for time-consuming buffer layer formation while maintaining high crystalline quality.
Solution Approach 2:
The invention performs preliminary action by selecting a first substrate that is lattice-matched to the semiconductor material before growth begins. This preliminary selection of substrates with matching lattice constants eliminates the need for subsequent buffer layer formation, reducing manufacturing steps.
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 enables a shorter manufacturing process for integrated circuits with high thermal conductivity substrates while maintaining high crystalline quality and heat dissipation performance by integrating the resistive element closer to the substrate, thus reducing the overall processing time.
Implementation Method 1
heat generated in the elements of a heterojunction bipolar transistor is dissipated through interconnects connected to the heterojunction bipolar transistor or a substrate immediately beneath the elements. Particularly, heat dissipation through the substrate is important
Implementation Method 2
a metal layer that is made of metal, and is formed on the resistive material layer so as to be in contact with the resistive material layer, the metal layer being formed in a first region and a third region
Data Source
AI summary
An integrated circuit includes a resistive material layer formed on a substrate, a metal layer formed on the resistive material layer, a bipolar transistor formed on the substrate, and a resistive element formed on the substrate. The bipolar transistor includes, as a sub-layer, the metal layer formed in a first region, and also includes a collector layer formed on the sub-collector layer. The resistive element is constituted by the resistive material layer formed in a second region.