Backside Illumination Sensor Bonding Pad Dielectric Mesa Structure
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Solution Overview
Problem
Semiconductor bonding pads, particularly in CMOS image sensors, face issues with peeling and defects due to the need for both sufficient size and strength to withstand physical contact, while also requiring thin metal layers for specific applications.
Innovation Solution
A method for forming a semiconductor structure with a bonding pad that includes a dielectric mesa interposed between the bonding pad and the metal layer, which enhances mechanical strength and prevents cracking and peeling by integrating the bonding pad with the interconnect structure, using a process that involves forming a trench in the dielectric material layer and depositing a metal layer on the mesa.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If thin metal layers are used for bonding pads, then the device meets specific application requirements for thin layers, but the bonding pads exhibit peeling and other defects
Solution Approach 1:
The bonding pad structure is segmented into multiple functional layers: a thin metal layer for electrical function, a thick underlayer for mechanical strength, and a dielectric mesa for structural support. This segmentation allows each layer to specialize in its primary function while working together as a unified structure.
Solution Approach 2:
The bonding pad employs a composite structure combining metal material for electrical conductivity, dielectric material for mechanical support, and potentially different metal alloys in the underlayer. This composite approach integrates materials with complementary properties to simultaneously achieve thin profile and high reliability.
2Strength
If bonding pads are made larger to withstand physical contact, then mechanical strength improves, but the overall device size increases
Solution Approach 1:
The solution transitions from a two-dimensional area-based strength approach to a three-dimensional vertical structure. The dielectric mesa and thick underlayer provide mechanical strength in the vertical dimension, allowing the bonding pad footprint to remain small while maintaining high mechanical strength through increased height and structural support.
3Ease of manufacture
If the bonding pad structure is simplified, then manufacturing complexity decreases, but the bonding pad cannot withstand physical contact forces
Solution Approach 1:
The dielectric mesa and thick underlayer are formed in advance before the thin metal bonding pad layer is deposited. This preliminary action creates a pre-formed mechanical support structure that protects the thin metal layer, allowing the bonding pad to withstand physical contact forces without requiring complex reinforcement of the metal layer itself.
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
The solution effectively inhibits cracking and peeling of the bonding pad, ensuring strong mechanical strength and reliable electrical connections, even under pressure, thereby addressing the defects associated with thin metal layers in semiconductor devices.
Implementation Method 1
depositing a metal layer on the mesa
Data Source
AI summary
The present disclosure provides one embodiment of a semiconductor structure. The semiconductor structure comprises a device substrate having a front side and a back side; an interconnect structure disposed on the front side of the device substrate; and a bonding pad connected to the interconnect structure. The bonding pad comprises a recessed region in a dielectric material layer; a dielectric mesa of the dielectric material layer interposed between the recessed region; and a metal layer disposed in the recessed region and on the dielectric mesa.