Copper Interconnect Anti-Diffusion Layers for Solid State Imaging
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Solution Overview
Problem
Solid state imaging apparatuses using copper interconnects face issues with copper diffusion into the substrate, leading to increased dark current and white blemishes, as well as light leakage due to interconnect thickness variations and dishing phenomena.
Innovation Solution
The implementation of a copper-containing interconnect layer with first and second anti-diffusion layers to prevent copper diffusion, combined with a stress-relieving film and a light-shielding interconnect layer to reduce dark current and white blemishes, and improve light-shielding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper interconnects are used to reduce resistance and improve high-speed operation, then electrical performance is improved, but copper diffusion into the substrate occurs causing increased dark current and white blemishes
Solution Approach 1:
A barrier metal layer is introduced as an intermediary between the copper interconnect and the semiconductor substrate. This barrier layer prevents copper atoms from diffusing into the substrate while maintaining electrical conductivity, thereby eliminating dark current and white blemishes caused by copper contamination.
Solution Approach 2:
The interconnect structure is designed as a composite material system consisting of multiple layers including copper interconnect, barrier metal layer, and capping layer. Each layer serves specific functions: copper provides low resistance, barrier metal prevents diffusion, and capping layer provides mechanical protection and stress relief.
2Reliability
If copper interconnects are used to reduce resistance, then electrical performance is improved, but dishing phenomena occur causing interconnect thickness variations and light leakage
Solution Approach 1:
The capping layer is designed with specific thickness parameters (50-200 nm) and material properties to compensate for dishing effects. By controlling the capping layer thickness and using appropriate materials, the overall interconnect structure maintains uniform effective thickness despite underlying dishing in the copper layer.
Solution Approach 2:
The capping layer is applied beforehand to the copper interconnect structure to cushion and compensate for potential dishing phenomena during subsequent CMP processing. This pre-protection layer ensures that the final interconnect structure maintains uniform thickness and prevents light leakage.
3Object-generated harmful factors
If multiple anti-diffusion layers are added to prevent copper diffusion, then copper contamination is reduced, but device structure complexity increases
Solution Approach 1:
The barrier metal layer is selectively applied only in regions where copper diffusion is a concern, such as at the interfaces between copper interconnect and semiconductor substrate. This localized approach provides effective diffusion protection while minimizing the addition of structural complexity to areas where it is not needed.
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 solution effectively reduces dark current and white blemishes, enhances light-shielding reliability, and maintains interconnect layer integrity, resulting in improved image quality and performance for solid state imaging devices.
Implementation Method 1
copper diffusion into the substrate, leading to increased dark current and white blemishes
Implementation Method 2
film stress produced between the first anti-diffusion layer and the photoelectric conversion section
Data Source
AI summary
A semiconductor device of the present invention includes a substrate; an imaging region which is formed at part of the substrate and in which photoelectric conversion cells including photoelectric conversion sections are arranged in the form of an array; a control-circuit region which is formed at part of the substrate and in which the imaging region is controlled and a signal from the imaging region is outputted; and a copper-containing interconnect layer formed above the substrate and made of a material containing copper. Furthermore, a first anti-diffusion layer and a second anti-diffusion layer are formed, as anti-diffusion layers for preventing the copper from diffusing into each photoelectric conversion section, on the photoelectric conversion section and the copper-containing interconnect layer, respectively.