Tungsten ILD Shielding for CMOS Memory Node Light Leakage
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Solution Overview
Problem
Current metal light-shielding technologies in Global Shutter CMOS image sensors provide limited improvement in reducing parasitic light leakage to memory nodes, which contaminates photo-generated charges and causes artifacts, and may cause plasma damage during fabrication.
Innovation Solution
A method involving a metal light-shielding structure fabricated over the memory node using a tungsten metal layer in the interlayer dielectric layer, aligned with the charge storage region to prevent incident light from reaching the memory node, and simultaneously formed with via contacts to avoid additional fabrication steps and plasma damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If metal light-shielding is engineered on the memory node, then light leakage reduction is improved, but plasma damage to the memory node occurs during fabrication
Solution Approach 1:
The light-shielding function is moved from the memory node level to the lens level by forming a light-shielding layer in the lens layer. This dimensional shift allows light blocking to occur before light reaches the memory node, eliminating the need for metal light-shielding on the memory node itself and avoiding plasma damage while still achieving light leakage reduction
Solution Approach 2:
The light-shielding layer is formed in advance during the lens fabrication process, before the memory node is exposed to plasma processing. This preliminary light shielding prevents parasitic light from reaching the memory node during subsequent fabrication steps, achieving both light leakage reduction and protection of the memory node
2Object-affected harmful factors
If separate fabrication steps are used for light-shielding and via contacts, then light leakage reduction is improved, but device complexity and manufacturing steps increase
Solution Approach 1:
The light-shielding layer and via contact structures are formed simultaneously in the same fabrication step using a single patterned layer. This merging of functions into one structural element and one fabrication step reduces process complexity while achieving both light shielding and electrical connectivity functions
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
Effectively reduces light leakage to the memory node, minimizing charge contamination and improving image quality without causing plasma damage during fabrication.
Implementation Method 1
A method involving a metal light-shielding structure fabricated over the memory node using a tungsten metal layer in the interlayer dielectric layer, aligned with the charge storage region to prevent incident light from reaching the memory node
Data Source
AI summary
Disclosed is a CMOS image sensor with global shutters and a method for fabricating the CMOS image sensor. In one embodiment, a semiconductor device, includes: a light-sensing region; a charge-storage region; a light-shielding structure; and at least one via contact; wherein the charge-storage region is spatially configured adjacent to the light-sensing region in a lateral direction, wherein the light-shielding structure is configured over the charge-storage region in a vertical direction so as to prevent incident light leaking from the light-sensing region to the signal-processing region, wherein the light-shielding structure is configured in an interlayer dielectric (ILD) layer, and wherein the light-shielding structure is simultaneously formed with the at least one via contact.