Solid-State Imaging Device Etching Protection
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Solution Overview
Problem
The manufacturing process of rear-surface irradiation type solid-state imaging devices faces challenges with the excessive etching of alignment marks and insulating layers, leading to visibility issues and potential short circuits due to the use of SiO and SiN materials, which result in unevenness and voids, affecting the reliability of the device.
Innovation Solution
A solid-state imaging device with a protective film resistant to etching is used to cover the insulating material, preventing excessive etching and ensuring reliable insulation, while maintaining the same number of processes, utilizing silicon nitride as the insulating material and forming protective films simultaneously with element isolation portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SiO or SiN materials are used as insulating material in the alignment mark and electrode pad region, then insulation property is improved, but excessive etching occurs during manufacturing leading to visibility issues and potential short circuits
Solution Approach 1:
The insulating layer is segmented into two distinct parts: the alignment mark portion and the electrode pad portion. This segmentation allows each portion to have optimized characteristics - the alignment mark can maintain visibility while the electrode pad provides reliable insulation, resolving the contradiction between insulation property and manufacturing precision.
Solution Approach 2:
Different regions of the insulating layer are given different properties. The alignment mark region uses material composition and thickness optimized for visibility and etching control, while the electrode pad region uses material optimized for insulation. This local differentiation resolves the contradiction by allowing each region to perform its specific function optimally.
2Reliability
If SiO or SiN materials are used as insulating material, then insulation is improved, but unevenness and voids occur during etching process
Solution Approach 1:
The material parameters of the insulating layer are changed by using a composite structure with different materials (such as silicon oxide and silicon nitride) in different regions. This parameter change allows the alignment mark region to have controlled etching characteristics while maintaining insulation, and the electrode pad region to provide reliable insulation without excessive etching, thus resolving the contradiction between reliability and etching uniformity.
3Reliability
If the substrate is reversed and color filter layer or on-chip lens is formed on the rear surface side, then focusing efficiency is improved, but alignment mark formation and electrode pad connection become more complex
Solution Approach 1:
The insulating layer is formed preliminarily on the front surface side of the substrate before the substrate is reversed. This preliminary action allows the alignment mark and electrode pad structures to be prepared in advance, simplifying the subsequent rear surface processing. The alignment mark can be formed using the pre-prepared insulating layer as a reference, and the electrode pad connection is facilitated by the pre-formed insulating structure, thus resolving the contradiction between focusing efficiency and process complexity.
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 enhances the reliability of the solid-state imaging device by preventing unnecessary etching of insulating layers and maintaining insulation, thereby improving yield and preventing voids, without increasing the number of manufacturing processes.
Implementation Method 1
an insulating material formed of silicon nitride is buried so as to form an insulating layer
Implementation Method 2
a protective film that is resistant to etching covering one end of the insulating material on an interior side of the semiconductor layer
Data Source
AI summary
A solid state imaging device including a semiconductor layer, an insulating material in an opening penetrating a surface of the semiconductor layer, and a protective film that is resistant to etching covering one end of the insulating material on an interior side of the semiconductor layer.