Thermal Inkjet Printhead Etch Stop Layer CMOS MEMS Integration
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Solution Overview
Problem
The high investment required for setting up silicon foundries to manufacture advanced thermal inkjet printheads limits small-scale production, leading to the use of outdated technologies in industrial printing, where high integration levels and special materials are needed but not economically justified.
Innovation Solution
A method for forming a thermal inkjet printhead using a semiconductor wafer with a pre-fabricated integrated circuit and thermal actuator section, where a thermal insulating layer and metal layers are used as an etch stop, allowing for cost-effective production by integrating CMOS and MEMS technologies without requiring heavy investment in full custom processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If complete manufacturing processes for high integration printhead actuators are carried out using specialized silicon foundries, then manufacturing precision and device performance are improved, but investment cost increases significantly
Solution Approach 1:
The manufacturing process is divided into two independent segments: standard CMOS logic circuit fabrication performed by conventional foundries, and thermal actuator element fabrication performed by specialized foundries. This segmentation allows each segment to be optimized independently while reducing overall investment requirements.
Solution Approach 2:
The semiconductor wafer is prepared in advance with all CMOS circuit layers (logic, power, thermal insulation) completed before transfer to the specialized foundry. This preliminary action enables the specialized foundry to focus only on the actuator fabrication, reducing their equipment requirements and investment cost.
2Ease of manufacture
If standard CMOS technology is used for electronic circuitry, then ease of manufacture and investment cost are improved, but manufacturing precision for thermal actuators deteriorates
Solution Approach 1:
A transfer interface is introduced between the standard CMOS foundry and the specialized MEMS foundry. The pre-fabricated wafer with completed CMOS layers serves as the intermediary that carries all necessary circuit structures to the second foundry, which then adds the actuator elements with high precision.
Solution Approach 2:
Different regions of the wafer receive different levels of processing quality: the CMOS circuit region is fabricated with standard precision by conventional foundries, while the actuator region receives enhanced precision processing at the specialized foundry. This local differentiation optimizes both cost and performance.
3Stability of the object's composition
If thermal insulation layers are made thicker to improve thermal stability, then thermal stability is improved, but energy transfer efficiency to ink deteriorates
Solution Approach 1:
The thermal insulation layer parameters are precisely controlled within an optimal range (500-2000 nm thickness) rather than simply increasing thickness. This parameter optimization ensures sufficient thermal stability for the CMOS circuits while maintaining adequate energy transfer efficiency to the ink for droplet ejection.
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 enables the production of high-performance thermal inkjet printheads with low investment costs, leveraging standard CMOS technology for electronic circuitry and specialized MEMS components, facilitating efficient energy transfer and ink ejection while maintaining thermal stability and mechanical robustness.
Implementation Method 1
etching a heater section for forming a thermal actuator element down to the first metal layer such that the first metal layer is acting as an etch stop layer
Implementation Method 2
the integrated circuit comprising at least a thermal insulating layer formed over a substrate
Implementation Method 3
The heaters 2 may be made of a resistive film
Data Source
AI summary
The present invention provides a method for forming a thermal inkjet printhead, comprising at least the following steps: providing a semiconductor wafer including an integrated electronic circuit and a section for forming a thermal actuator element, the integrated circuit comprising at least: a thermal insulating layer formed over a substrate; and a first metal layer formed over the thermal insulating layer; wherein the first metal layer extends into the section for forming the thermal actuator element; and etching a section for forming a thermal actuator element to the first metal layer such that the first metal layer is acting as an etch stop layer. Further there is provided a thermal inkjet printhead formed by a method of the present invention and a semiconductor wafer for forming the thermal inkjet printheads by a method of the present invention.