LED Sidewall Contact Structure With Positive Photoresist Spacer
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Solution Overview
Problem
Existing light emitting diode (LED) devices face challenges in achieving efficient light emission and reliable electrical contact due to issues with photoresist material usage and sidewall contact configurations.
Innovation Solution
The proposed solution involves a light emitting device design that includes a backplane with an array of LEDs, a positive tone, imageable dielectric material layer (such as a positive photoresist) with a reentrant vertical cross-sectional profile, and a conductive sidewall contact. This design ensures a seamless interface between the LEDs and the photoresist layer, preventing moisture ingress and allowing for efficient light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional photoresist material and sidewall contact configuration are used, then the device structure is simpler, but light emission efficiency is reduced due to opaque structures obstructing light paths
Solution Approach 1:
The patent removes the opaque metal contact material from the sidewall region and replaces it with a transparent conductive oxide layer. This extraction of the harmful opaque material allows light to pass through the sidewall contact region without obstruction, directly improving light emission efficiency while maintaining the necessary electrical contact function through the transparent conductive material.
Solution Approach 2:
The patent changes the optical parameter (transparency) of the contact material by transitioning from opaque metal to transparent conductive oxide. This parameter change allows the contact structure to simultaneously fulfill both electrical conduction and optical transparency requirements, resolving the contradiction between structural simplicity and light emission efficiency.
2Reliability
If a conventional photoresist material is used, then the manufacturing process is simpler, but moisture ingress occurs at the LED-photoresist interface
Solution Approach 1:
The patent employs a composite photoresist structure consisting of a first photoresist layer and a second photoresist layer with different material compositions and properties. The first layer provides good planarization and coverage, while the second layer provides superior moisture barrier properties and adhesion to the LED sidewalls. This composite approach creates a seamless interface that prevents moisture ingress while maintaining manufacturing feasibility.
Solution Approach 2:
The patent applies different photoresist materials with specific local qualities to different regions and functions. The first photoresist layer is optimized for planarization and uniform coverage, while the second photoresist layer is specifically designed with enhanced moisture barrier properties at the critical LED-photoresist interface region. This local differentiation of material properties addresses the moisture ingress issue without requiring complete redesign of the entire photoresist system.
3Illumination intensity
If light-absorbing materials are used in the sidewall contact, then electrical contact is achieved, but light emission performance deteriorates
Solution Approach 1:
The patent introduces a transparent conductive oxide material as an intermediary between the metal contact layer and the external environment. This intermediary material maintains the electrical conduction pathway while being optically transparent, allowing light to pass through without absorption. The transparent conductive oxide acts as a mediator that reconciles the conflicting requirements of electrical contact and light transmission.
Data Source
AI summary
A light emitting device includes a backplane, an array of light emitting diodes attached to a frontside of the backplane, a positive tone, imageable dielectric material layer, such as a positive photoresist layer, located on the frontside of the backplane and laterally surrounding the array of light emitting diodes, such that sidewalls of the light emitting diodes contacting the positive tone, imageable dielectric material layer have a respective reentrant vertical cross-sectional profile, and at least one common conductive layer located over the positive tone, imageable dielectric material layer and contacting the light emitting diodes.