Silicon Nitride Ring for Self-Aligned Bipolar Transistor Base
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Solution Overview
Problem
The existing methods for manufacturing self-aligned bipolar transistors with a sacrificial nitride emitter and a raised external base require complex process steps, such as selective epitaxial growth and chemical mechanical polishing, increasing manufacturing costs and time.
Innovation Solution
A silicon nitride ring is formed around a sacrificial emitter using a simultaneous deposition and etch process, providing support for a raised external base without the need for these complex steps, and is subsequently etched away to form an emitter window for a polysilicon emitter structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If selective epitaxial growth and chemical mechanical polishing procedures are used to form a self aligned bipolar transistor with a sacrificial nitride emitter and a raised external base, then the transistor achieves better window downscaling and lower parasitic capacitances and resistances, but the manufacturing cost and processing time increase significantly
Solution Approach 1:
The patent extracts and removes the complex selective epitaxial growth and chemical mechanical polishing steps from the manufacturing process. Instead, it uses a simplified approach where a sacrificial nitride emitter and silicon nitride ring are formed by depositing silicon nitride material and performing a single etch process to simultaneously create both structures, eliminating the need for multiple complex process steps while maintaining the self-aligned bipolar transistor architecture
Solution Approach 2:
The patent segments the manufacturing process into distinct functional components: the sacrificial nitride emitter, the silicon nitride ring, and the raised external base. These segments are formed separately but simultaneously through the deposition and etching process, allowing each component to be optimized independently while reducing overall process complexity
2Reliability
If complex process steps like selective epitaxial growth and chemical mechanical polishing are employed, then self aligned bipolar transistors with raised external base can be manufactured, but the device complexity and manufacturing complexity increase
Solution Approach 1:
The patent merges the formation of the sacrificial nitride emitter and the silicon nitride ring into a single deposition and etching process. By depositing a layer of silicon nitride material over the active area and performing one etch process, both structures are created simultaneously, reducing the number of process steps while maintaining the precise self-aligned geometry required for reliable transistor operation
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 improves compatibility with BiCMOS technology, achieving high radio frequency performance without the need for costly and time-consuming processes like CMP and selective epitaxial growth.
Implementation Method 1
The silicon nitride ring provides support for forming a raised external base for the transistor
Implementation Method 2
The sacrificial emitter and the silicon nitride ring are then subsequently etched away and an emitter window is formed for the transistor
Data Source
AI summary
A system and method are disclosed for providing a self aligned bipolar transistor using a silicon nitride ring. An active region of the transistor is formed and a sacrificial emitter is formed above the active region of the transistor. A silicon nitride ring is formed around the sacrificial emitter. The sacrificial emitter and the silicon nitride ring are formed by depositing a layer of silicon nitride material over the active area of the transistor and performing an etch process to simultaneously create both the sacrificial emitter and the silicon nitride ring. The silicon nitride ring provides support for forming a raised external base for the transistor.