Backside Sub-Collector Contact for SiGe HBT Heat and Capacitance
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Solution Overview
Problem
SiGe HBT devices in 3D integration suffer from excessive self-heating and performance degradation due to high collector to base capacitance and resistance, which are not effectively addressed by existing technologies.
Innovation Solution
A heterojunction bipolar transistor (HBT) with a backside sub-collector contact is integrated with a CMOS device, utilizing a direct connection through an insulator layer, reducing self-heating and collector resistance, and employing a simplified manufacturing process with reduced masking steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If SiGe HBT devices are integrated in 3D process, then power dissipation increases, but self-heating becomes excessive and performance degrades
Solution Approach 1:
The patent transitions from conventional planar contact geometry to a three-dimensional configuration by extending the contact structure vertically through the collector region. This dimensional change allows heat to dissipate through additional thermal pathways in the vertical direction, effectively reducing self-heating while maintaining high power dissipation capability.
Solution Approach 2:
The contact structure is segmented into multiple regions: a first contact region at the surface, a second contact region deeper in the substrate, and interconnected conductive paths. This segmentation creates distributed heat dissipation zones throughout the collector region, preventing heat concentration in a single location and reducing overall self-heating.
2Ease of manufacture
If conventional frontside contact is used, then manufacturing process is complex with multiple masking steps, but backside contact requires additional process steps
Solution Approach 1:
Instead of making contacts from the frontside of the wafer through sequential masking steps, the patent inverts the approach by forming contacts from the backside of the wafer. This inversion allows the contact structures to be defined in a single masking step on the backside, eliminating the need for multiple frontside masking operations and simplifying the overall manufacturing process.
3Reliability
If collector to base capacitance and resistance are high, then signal transmission is affected, but reducing them requires additional process complexity
Solution Approach 1:
The patent introduces an intermediate conductive structure that extends through the collector region, serving as a mediator between the surface contact and the base region. This intermediate structure provides optimized electrical pathways that reduce both capacitance and resistance by creating direct, low-impedance connections without requiring complex additional process steps.
Data Source
AI summary
The present disclosure relates to semiconductor structures and, more particularly, to heterojunction bipolar transistor wafers with backside sub-collector contact and methods of manufacture. The structure includes: a first chiplet comprising a first device with a backside contact; and a second chiplet connected to the first chiplet, the second chiplet comprising a second device with a frontside contact.