Film Stack Spacer Formation for Thermal Inkjet Print Heads
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Solution Overview
Problem
Conventional film stacks in thermal fluid ejector apparatuses, such as thermal inkjet print heads, face challenges with poor step coverage and chemical protection due to thick passivation layers, leading to thin spots and direct chemical paths to electrically-conductive elements.
Innovation Solution
The formation of spacers from a passivation layer, specifically using Silicon Nitride (SiN) and Silicon Carbide (SiC) materials, which are etched to increase dielectric thickness and improve step coverage, providing robust electrical and chemical insulation while maintaining thin passivation layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If thick passivation layers are used, then chemical protection is improved, but step coverage deteriorates and thin spots form
Solution Approach 1:
The passivation layer is segmented into two distinct functional layers: a first passivation layer (SiN) providing chemical protection and electrical insulation, and a second passivation layer (SiC) providing chemical protection. This segmentation allows each layer to be optimized for its specific function, with the first layer being thinner and more conformal, thus improving step coverage while maintaining chemical protection.
Solution Approach 2:
Different regions of the passivation structure are assigned different materials and thicknesses based on local requirements. The first passivation layer (SiN) is used where electrical insulation and conformal coverage are critical, while the second passivation layer (SiC) is used where chemical resistance is the primary concern. This local differentiation resolves the contradiction by matching material properties to specific functional needs.
2Object-affected harmful factors
If thick passivation layers are used, then chemical protection is improved, but dielectric thickness is reduced due to poor step coverage
Solution Approach 1:
The passivation system is divided into two layers with the first layer (SiN) being thinner and more conformal, allowing it to maintain adequate dielectric thickness in stepped regions. The second layer (SiC) is added for chemical protection without compromising the dielectric thickness established by the first layer, thus resolving the contradiction between chemical protection and dielectric thickness maintenance.
Solution Approach 2:
The invention changes the material parameter of the passivation layers, using Silicon Nitride (SiN) for the first layer which provides better conformal coverage and electrical insulation properties. This material parameter change allows the first layer to be thinner while maintaining adequate dielectric thickness, and the second Silicon Carbide (SiC) layer is added for chemical protection.
3Manufacturing precision
If thin passivation layers are used, then step coverage is improved, but direct chemical paths form to electrically-conductive elements
Solution Approach 1:
The passivation function is segmented between two layers: the first SiN layer provides electrical insulation and conformal coverage with good step coverage, while the second SiC layer provides the chemical protection that would be insufficient in a thin single layer. This segmentation allows each layer to be optimized for its primary function without compromise.
Solution Approach 2:
The invention uses a composite passivation structure combining two different materials (SiN and SiC) with complementary properties. SiN provides conformal coverage and electrical insulation, while SiC provides enhanced chemical resistance. This composite approach allows thin layers to achieve both good step coverage and adequate chemical protection.
4Reliability
If thick passivation layers are used, then electrical insulation is improved, but thermal performance deteriorates
Solution Approach 1:
The electrical insulation function is segmented to the first SiN passivation layer, which is kept thin to maintain thermal performance. The second SiC layer is added for chemical protection rather than relying on increased thickness for electrical insulation. This segmentation allows adequate electrical insulation with minimal thickness, preserving thermal performance.
Solution Approach 2:
The invention changes the material parameter from using a single thick passivation layer to a composite of two thinner layers with different material properties. The SiN layer provides electrical insulation with better thermal conductivity than thicker alternatives, and the SiC layer provides chemical protection, collectively achieving the required electrical insulation with improved thermal performance.
Data Source
Figure 1A~1B
Figure 1C~1D
Figure 2
AI summary
A method of manufacturing a plurality of spacers in a film stack includes forming at least one electrically-conductive element having sidewalls on a substrate, depositing a plurality of passivation layers proximate to the substrate, and performing etching on one of the plurality of passivation layers to form a plurality of spacers substantially across from the sidewalls of the at least one electrically-conductive element.