Bipolar Transistor Base Wire Disconnection Prevention
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Solution Overview
Problem
Conventional semiconductor devices have limited flexibility in the layout of bipolar transistors and circuit elements due to restrictions on the direction in which the base wire is extended, leading to potential disconnection issues and reduced yield.
Innovation Solution
The semiconductor device employs a single-crystal semiconductor substrate with inverted and forward mesa steps, allowing the base wire to intersect at a disconnection prevention structure, enabling the base wire to extend in directions orthogonal to each other, thereby enhancing the layout freedom and reducing disconnection risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the base wire is extended in a conventional direction crossing an edge with inverted mesa surface, then the layout is simple, but the base wire may disconnect and layout freedom is restricted
Solution Approach 1:
The patent applies local quality by creating different mesa surface orientations at different locations. Specifically, the edge of the collector layer is configured to have a forward mesa surface at the position where the base wire crosses, while other edges maintain inverted mesa surfaces. This localized change in surface orientation prevents base wire disconnection at the critical crossing point while maintaining the desired layout flexibility.
Solution Approach 2:
The patent employs asymmetry by making the mesa surface orientation asymmetric with respect to the base wire crossing. The collector layer edge is designed such that the mesa surface facing the base wire direction has a forward slope, while opposite edges have inverted slopes. This asymmetric configuration ensures reliable base wire connection in the specific direction needed for layout freedom.
2Manufacturing precision
If anisotropic etching is used to form inverted mesa steps, then crystal plane orientation control is achieved, but base wire disconnection occurs when wires cross inverted mesa edges
Solution Approach 1:
The patent maintains the precision benefits of anisotropic etching by applying it selectively. The collector layer is etched to form inverted mesa surfaces at most edges for precise dimensional control, but the specific edge crossed by the base wire is configured to have a forward mesa surface, preventing disconnection while preserving manufacturing precision elsewhere.
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 configuration allows for linear connection of circuit elements to bipolar transistors, reduces disconnection occurrences, and increases the degree of freedom in layout, improving the reliability and efficiency of semiconductor device design.
Implementation Method 1
a single-crystal semiconductor substrate with an upper surface including a first direction in which an inverted mesa step extends and a second direction in which a forward mesa step extends in response to anisotropic etching in which an etching rate depends on crystal plane orientation
Implementation Method 2
a first bipolar transistor including a first collector layer, a first base layer, and a first emitter layer that are epitaxially grown on the semiconductor layer
Data Source
AI summary
On a single-crystal semiconductor substrate with an upper surface including a first direction in which an inverted mesa step extends and a second direction in which a forward mesa step extends in response to anisotropic etching in which an etching rate depends on crystal plane orientation, a bipolar transistor including a collector layer, a base layer, and an emitter layer that are epitaxially grown, and a base wire connected to the base layer are arranged. A step is provided at an edge of the base layer, and the base wire is extended from inside to outside of the base layer in a direction intersecting the first direction in a plan view. An intersection of the edge of the base layer and the base wire has a disconnection prevention structure that makes it difficult for step-caused disconnection of the base wire to occur.