Image Sensor BEOL Planarization via Metal Dummy Patterns
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Solution Overview
Problem
The manufacturing process of image sensors is complex and expensive due to the need for non-uniform metal BEOL layer distribution to avoid interference with light-detecting elements, requiring extensive steps including chemical-mechanical planarization (CMP), which limits production efficiency and cost-effectiveness.
Innovation Solution
Incorporating a planarizing metal dummy pattern in the BEOL layer to form a passive optical element that provides a uniform metal distribution and enhances light detection, allowing for reduced production steps and potentially cheaper fabrication by using metal patterns above light-detecting elements to act as passive optical components like lenses or filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If metal BEOL layers are designed to avoid being arranged above light-detecting elements, then light interference is prevented, but non-uniform material deposition is formed requiring extensive CMP steps
Solution Approach 1:
The patent segments the metal BEOL layer into two functional parts: (1) metal wiring patterns positioned laterally to avoid light interference with photodiodes, and (2) separate metal dummy patterns positioned above the photodiodes specifically for planarization. This segmentation allows each part to fulfill its specific function without compromising the other.
Solution Approach 2:
The metal dummy patterns serve multiple functions simultaneously: they provide planarization to achieve uniform material deposition for subsequent CMP steps, and they maintain electrical connectivity through the BEOL structure. This multi-functionality reduces the need for separate dedicated planarization layers.
2Manufacturing precision
If metal BEOL layers are arranged above light-detecting elements to provide uniform material distribution, then deposition uniformity is improved, but light interference with light-detecting elements occurs
Solution Approach 1:
The patent segments the metal BEOL layer into two functional parts: (1) metal wiring patterns positioned laterally to avoid light interference with photodiodes, and (2) separate metal dummy patterns positioned above the photodiodes specifically for planarization. This segmentation allows each part to fulfill its specific function without compromising the other.
3Manufacturing precision
If extensive CMP steps are performed between deposition of each BEOL layer, then planarization is achieved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent performs preliminary planarization action by incorporating metal dummy patterns during the metal BEOL layer deposition itself, before subsequent deposition steps. This preliminary planarization provides a sufficiently uniform surface for subsequent processing, reducing the need for extensive intermediate CMP steps.
Solution Approach 2:
The patent merges the planarization function with the metal BEOL layer deposition process by including metal dummy patterns in the same deposition step. This combining of functions eliminates the need for separate planarization steps between metal layer depositions.
4Productivity
If the number of manufacturing steps is reduced, then production efficiency and cost-effectiveness improve, but manufacturing precision may be compromised
Solution Approach 1:
The patent performs preliminary planarization action by incorporating metal dummy patterns during the metal BEOL layer deposition itself, before subsequent deposition steps. This preliminary planarization provides a sufficiently uniform surface for subsequent processing, reducing the need for extensive intermediate CMP steps.
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 simplifies the production process by eliminating the need for intermediate planarization steps, reduces manufacturing costs, and improves pixel performance by increasing light intensity collection, while maintaining optical functionality without interfering with electrical connections.
Implementation Method 1
depositing of a metal dummy pattern in the BEOL layer simultaneously with forming of the metal wiring in the BEOL layer so as to planarize a density of the metal in the BEOL layer
Implementation Method 2
a metal pattern which forms a passive optical element is also formed in that BEOL layer
Data Source
Figure 1
Figure 2~3a
Figure 3b~3c
AI summary
A method for producing an image sensor comprises: depositing a first back-end-of-line, BEOL, layer above a substrate comprising an array of light-detecting elements, said BEOL layer comprising metal wirings being arranged to form connections to components on the substrate and together with depositing the first BEOL layer, improving planarization of the first BEOL layer by depositing a planarizing metal dummy pattern in the first BEOL layer, wherein a part of the planarizing metal dummy pattern is arranged above a light-detecting element, wherein the planarizing metal dummy patterns is formed from the same material as the metal wirings and is deposited to planarize density of the metal deposited in the first BEOL layer across a surface of the layer and wherein a shape and/or position of the metal dummy pattern above the array of light-detecting elements is designed to provide a desired effect on incident light.