Polyimide Planarization for Redistribution Layer Surface Flatness
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Solution Overview
Problem
In semiconductor devices like DRAM, the thick redistribution layers cause unevenness and height discrepancies in the polyimide layer, leading to issues such as corrosion and void formation during assembly, which can result in defective products and accelerated deterioration.
Innovation Solution
The method involves using a photo mask with specific light transmission and shading fields to control the exposure dose of a photosensitive polyimide resin, ensuring the polyimide layer thickness is uniform across different regions, thereby eliminating height differences and surface unevenness, and using this patterned layer as an etching mask for precise removal of insulating films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick redistribution layer is used in semiconductor devices, then the electrical connectivity and signal transmission are improved, but surface unevenness and height discrepancies are formed on the polyimide layer
Solution Approach 1:
The patent applies different exposure doses to different regions of the polyimide layer using a photo mask with variable light transmission. The first region (over thick redistribution layers) receives a lower exposure dose, while the second region (over thinner areas) receives a higher exposure dose, creating locally optimized polyimide thickness to compensate for underlying surface variations
Solution Approach 2:
The patent changes the exposure dose parameter across different regions of the polyimide layer by using a photo mask with spatially varying light transmission properties. This parameter modification allows the polyimide thickness to be adjusted locally, transforming the uniform exposure approach into a controlled variable exposure process that compensates for surface unevenness
2Ease of manufacture
If the polyimide layer thickness varies across regions, then the manufacturing process is simpler, but corrosion and void formation occur during assembly
Solution Approach 1:
The patent performs preliminary action by controlling the polyimide layer thickness through selective exposure before the assembly process. By pre-compensating for thickness variations through the photo mask exposure process, the patent prevents subsequent problems such as corrosion and void formation that would occur during assembly, eliminating the need for post-processing corrections
3Shape
If uniform polyimide layer thickness is achieved through conventional exposure, then the surface appears flat, but height differences between regions remain
Solution Approach 1:
The patent makes different parts of the polyimide layer have different exposure characteristics by using a photo mask with spatially varying light transmission. The first region receives reduced exposure to maintain thickness, while the second region receives full exposure for thinner areas, achieving both apparent flatness and actual thickness uniformity through localized exposure control
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 approach results in a reliable semiconductor device with reduced risk of corrosion and void formation, ensuring a flat surface for assembly and improved long-term reliability by maintaining uniform polyimide thickness and eliminating depressions, thus preventing infiltration and air bubble issues.
Implementation Method 1
a photo mask with specific light transmission and shading fields to control the exposure dose of a photosensitive polyimide resin
Data Source
AI summary
A semiconductor device includes a semiconductor substrate having a semiconductor substrate having a main surface including a first portion; a redistribution layer provided over the first portion of the main surface of the semiconductor substrate; an insulating layer covering the first portion of the main surface of the semiconductor substrate and the redistribution layer; and a first polyimide film covering the insulating layer; wherein the polyimide film has a substantially flat upper surface.