LCOS Structure with Peripheral Conductive Pad and Adhesive Bonding
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Solution Overview
Problem
Existing LCOS display devices face issues with low productivity and reliability due to cracks in metal layers caused by conductive metal particles piercing under vertical pressure during bonding, and bulkiness from glass substrates extending for peripheral circuitry connections.
Innovation Solution
An LCOS structure with a conductive backing pad exposed through an opening around the liquid crystal layer, electrically connected to the transparent conductive layer via conductive metal particles in an adhesive, eliminating metal layers under the pad and using a glass substrate for alignment layers to reduce size and enhance reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a wafer-level process with conductive adhesive is used to bond the transparent conductive layer to the silicon substrate, then productivity is improved, but the conductive metal particles in the adhesive pierce the metal layers under vertical pressure, causing cracks and reducing reliability
Solution Approach 1:
The patent removes the metal layers from under the bonding area where the conductive adhesive is applied. Specifically, the silicon substrate is designed with a structure where metal layers are present only in peripheral regions, not in the central bonding area. This extraction of metal layers eliminates the harm caused by conductive metal particles piercing through them during bonding, while still maintaining electrical connectivity through the conductive adhesive between the transparent conductive layer and the conductive pad on the silicon substrate.
2Ease of operation
If glass substrate portions extend beyond the silicon substrate to accommodate peripheral circuitry connections, then ease of connection is improved, but the device becomes bulky
Solution Approach 1:
The patent repositions the bonding area and electrical connection interface to the periphery of the device rather than requiring extended glass substrate portions. The conductive pad is arranged at the peripheral region of the silicon substrate, allowing electrical connections to be made at the edge of the device. This dimensional reorganization enables peripheral circuitry connections without requiring the glass substrate to extend significantly beyond the silicon substrate, thereby reducing bulkiness while maintaining ease of connection.
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 design allows for internal signal leading, reduced size, and increased reliability by preventing damage to metal layers during bonding and minimizing bulkiness, while maintaining high-pressure resistance and effective electrical connectivity.
Implementation Method 1
the transparent conductive layer is electrically connected to the conductive backing pad by conductive metal particles in the conductive adhesive
Data Source
AI summary
The present invention provides a LCOS structure and a method for fabricating same. The LCOS structure includes: a silicon substrate; a liquid crystal layer and a transparent conductive layer both disposed above the silicon substrate. In the silicon substrate, there are formed a conductive pad, an opening where the conductive pad is exposed, and at least one metal layer. The opening is located peripherally around the liquid crystal layer, there is no portion of the metal layer located under the conductive pad. The conductive backing is located at the same vertical level as one metal layer in the at least one metal layer and electrically connected thereto, a conductive adhesive fills in the opening and a gap between the silicon substrate and the transparent conductive layer. The transparent conductive layer is electrically connected to the conductive pad by conductive metal particles in the conductive adhesive.