Semiconductor Contact Pads with Reflective Structures for Light Management
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Solution Overview
Problem
Semiconductor devices, particularly silicon chips used with light emitting diodes (LEDs), face issues with leakage currents due to absorption of scattered light, which can lead to erratic circuit functioning and parasitic effects from high-intensity radiation during the laser-lift-off process.
Innovation Solution
The implementation of reflective and absorptive structures between the uppermost metal level and contact pads on semiconductor devices, composed of different materials than the contact pads and metal lines, to reflect or absorb light, thereby preventing light from entering the substrate and minimizing parasitic effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If contact pads are disposed at the major surface of the semiconductor device, then electrical connection is achieved, but light-induced leakage currents occur due to light absorption
Solution Approach 1:
Reflective structures are introduced as intermediary elements between the contact pads and the semiconductor substrate. These reflective structures reflect incident light away from the substrate, preventing light absorption that would generate leakage currents, while allowing the contact pads to maintain their electrical connection function.
Solution Approach 2:
The contact pad structure is segmented into multiple functional regions: the contact pad itself for electrical connection, reflective structures for light management, and isolation regions for electrical separation. This segmentation allows each component to perform its specific function without interference from light-induced effects.
2Object-affected harmful factors
If reflective structures are added between the upper metal level and contact pads, then light-induced leakage currents are prevented, but device complexity increases
Solution Approach 1:
The reflective structures are merged with the existing metallization layers and contact pad structures. By integrating the light-reflecting function into the existing device architecture rather than adding completely separate components, the increase in complexity is minimized while still achieving effective light management.
Solution Approach 2:
The uppermost metal level serves multiple functions: it provides electrical interconnection and simultaneously acts as a reflective structure for light management. This multi-functionality reduces the need for additional dedicated components, thereby limiting the increase in device complexity.
3Reliability
If isolation regions are used to separate contact pads, then electrical isolation is achieved, but light can still enter the substrate through gaps between contact pads
Solution Approach 1:
Reflective structures are positioned in the gaps between contact pads to act as intermediaries that redirect incident light. These structures prevent light from reaching the semiconductor substrate through the isolation regions, thereby eliminating the source of leakage currents while maintaining electrical isolation.
Solution Approach 2:
The reflective structures are selectively placed in specific locations where light would otherwise enter the substrate through isolation regions. This localized approach ensures that light management is optimized at the critical interfaces without requiring modification of the entire device structure.
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 solution effectively prevents light-induced leakage currents and parasitic effects, ensuring stable operation of semiconductor devices by reflecting or absorbing light across a wide range of wavelengths, thus enhancing the reliability of LED applications.
Implementation Method 1
Reflective structures are disposed between the upper metal level and the contact pads, where each of the reflective structures that is directly over the active region completely overlaps an associated portion of the isolation region separating the contact pad
Implementation Method 2
light absorptive structures disposed between the upper metal level and the contact pads, where the light absorptive structures include an amorphous semiconductor material
Data Source
AI summary
A semiconductor device includes an active region disposed in a semiconductor substrate and an uppermost metal level including metal lines, where the uppermost metal level is disposed over the semiconductor substrate. Contact pads are disposed at a major surface of the semiconductor device, where the contact pads are coupled to the metal lines in the uppermost metal level. An isolation region separates the contact pads disposed at the major surface. Adjacent contact pads are electrically isolated from one another by a portion of the isolation region. Reflective structures are disposed between the upper metal level and the contact pads, where each of the reflective structures that is directly over the active region completely overlaps an associated portion of the isolation region separating the contact pad.