Self-Aligned Bipolar Transistor Using Sacrificial Polysilicon Base
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Solution Overview
Problem
The existing methods for manufacturing self-aligned bipolar transistors with a sacrificial nitride emitter and raised external base require complex process steps, such as selective epitaxial growth and chemical mechanical polishing, increasing costs and processing time, and are not compatible with BiCMOS technology.
Innovation Solution
A self-aligned bipolar transistor is manufactured using a sacrificial polysilicon external base, where an active region is formed, covered with a silicon oxide layer, and a polysilicon emitter structure is created after removing the sacrificial polysilicon base, eliminating the need for complex processes like CMP and selective epitaxial growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a sacrificial nitride emitter and raised external base are used to manufacture self-aligned bipolar transistors, then self-alignment and reduced parasitic capacitances are achieved, but complex process steps including selective epitaxial growth and chemical mechanical polishing are required
Solution Approach 1:
The patent extracts the sacrificial material function from nitride to polysilicon, allowing the base structure to be formed and then removed cleanly without requiring complex selective epitaxial growth or CMP processes. The polysilicon sacrificial base is deposited, patterned, and etched away to create the self-aligned structure.
Solution Approach 2:
The patent changes the material parameter from nitride to polysilicon for the sacrificial element, which fundamentally alters the manufacturing approach. Polysilicon can be deposited using standard CVD processes and removed with selective etching, eliminating the need for complex selective epitaxial growth and chemical mechanical polishing steps.
2Manufacturing precision
If complex process steps like selective epitaxial growth and chemical mechanical polishing are used, then self-aligned bipolar transistors are manufactured, but manufacturing cost and processing time increase
Solution Approach 1:
Changing the sacrificial material from nitride to polysilicon enables the use of standard deposition and etching processes instead of complex selective epitaxial growth and CMP, significantly reducing processing time and manufacturing cost while maintaining self-alignment precision.
Solution Approach 2:
The polysilicon sacrificial base serves as a temporary structure that is easily deposited and removed. This disposable approach eliminates the need for expensive and time-consuming complex processes, as the sacrificial material can be cleanly removed with selective etching without requiring CMP or selective epitaxial growth.
3Manufacturing precision
If a sacrificial nitride emitter and raised external base structure is used, then self-aligned bipolar transistors are achieved, but compatibility with BiCMOS technology is reduced
Solution Approach 1:
The patent changes the sacrificial material from nitride to polysilicon, which is compatible with BiCMOS fabrication processes. Polysilicon deposition and etching are standard steps in BiCMOS technology, allowing the self-aligned bipolar transistor structure to be integrated into BiCMOS circuits without process incompatibilities.
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 method simplifies the manufacturing process, reduces parasitic capacitances and resistances, and enhances compatibility with BiCMOS technology, achieving efficient and high-performance self-aligned bipolar transistors with reduced complexity and cost.
Implementation Method 1
An etch procedure is subsequently performed to remove the sacrificial polysilicon external base
Implementation Method 2
A layer of doped polysilicon material is deposited to fill a cavity within the transistor formed by the removal of the sacrificial polysilicon external base
Data Source
AI summary
A system and method are disclosed for providing a self aligned bipolar transistor using a sacrificial polysilicon external base. An active region of a transistor is formed and a sacrificial polysilicon external base is formed above the active region of the transistor and covered with a silicon oxide layer. Then an emitter window is etched and filled with silicon nitride. An etch procedure is subsequently performed to remove the sacrificial polysilicon external base. A layer of doped polysilicon material is then deposited to fill a cavity within the transistor formed by the removal of the sacrificial polysilicon external base. A polysilicon emitter structure is subsequently formed in the emitter window. The self aligned bipolar transistor architecture of the invention is compatible with BiCMOS technology.