IR Sensor Metal Trace Layout for Transmissivity
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Solution Overview
Problem
Conventional membrane IR sensors experience reduced transmissivity and reliability due to IR radiation reflection from metal traces, particularly in Wafer Level Chip Scale Package configurations, where metal traces block IR radiation from reaching the absorber.
Innovation Solution
The design involves forming polysilicon traces with a first width over a substrate, accompanied by a recess, and narrower metal traces over a dielectric layer, with reduced horizontal spacing to minimize the reflective area, thereby enhancing IR transmissivity. The metal traces are formed in a single or multiple metallization layers, and dielectric layers, such as silicon dioxide, are used to optimize the layout.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal traces are used in conventional membrane IR sensors, then electrical connectivity is achieved, but IR radiation is blocked or reflected away from the absorber, reducing transmissivity
Solution Approach 1:
The patent changes the physical parameters of the metal traces by reducing their width and minimizing the area they occupy on the substrate. This parameter change allows the metal traces to maintain their electrical connectivity function while reducing their harmful effect of blocking IR radiation, thereby improving sensor transmissivity without sacrificing reliability
Solution Approach 2:
The patent applies local quality by creating non-uniform metal trace configurations where the traces are narrower and occupy less area in regions where they would otherwise block IR paths. This localized modification optimizes the balance between electrical connectivity and IR transmissivity at specific critical locations on the substrate
2Reliability
If wider metal traces are used, then electrical conductivity is improved, but the reflective area increases, reducing IR transmissivity
Solution Approach 1:
The patent optimizes the width parameter of metal traces to achieve an optimal balance point. By reducing the trace width from conventional dimensions, the patent decreases the reflective area and improves IR transmissivity while maintaining sufficient electrical conductivity through careful trace routing and design
3Ease of manufacture
If standard metal trace layout is used, then manufacturing is simplified, but IR radiation is substantially blocked, affecting sensor performance
Solution Approach 1:
The patent modifies the standard manufacturing parameters by specifying reduced metal trace widths and optimized spacing. These parameter changes can be integrated into existing manufacturing processes while producing improved sensor performance, maintaining ease of manufacture through standard photolithography and metallization techniques
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 reduces the reflective area of metal traces by up to 50%, improving the responsivity and reliability of the IR sensor by allowing more IR radiation to reach the absorber.
Implementation Method 1
the IR sensor includes a thermopile and a plurality of sections
Implementation Method 2
reduces the reflective area of metal traces by up to 50%, improving the responsivity and reliability of the IR sensor by allowing more IR radiation to reach the absorber
Data Source
AI summary
In conventional membrane infrared (IR) sensors, little to no attention has been paid toward transmissivity of IR near metal traces. Here, because the substrate of an integrated circuit carrying the sensor is used as a visible light filter, reflection of IR radiation back into the substrate can affect the operation and reliability of the IR sensor. As a result, an arrangement is provided that reduces the area occupied by metal lines by reducing the pitch and compacting the routing so as to reduce the effects from the reflection of IR radiation by metal traces.