Backside Opening Formation for Ultra-Thin Semiconductor Die Singulation
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Solution Overview
Problem
The challenge lies in minimizing the vertical resistance of semiconductor die while maintaining structural integrity, as existing methods face difficulties in cutting through thick metal layers during the singulation process, leading to premature wear and excessive debris on saw blades.
Innovation Solution
A process involving the formation of backside openings and a honeycomb pattern of base substrate material to create ultra-thin semiconductor die, allowing for the lift-off of backside metal without cutting through thick metal layers, using techniques like isotropic etching and plasma etching to achieve precision and structural support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick metal layer is formed across the back surface to reduce vertical resistance, then the vertical resistance decreases, but cutting through the thick metal layer during singulation causes premature wear and excessive debris on the saw blade
Solution Approach 1:
The back surface metal layer is segmented into discrete regions: continuous metal regions over active die areas and interrupted metal regions over saw street areas. This segmentation allows the metal layer to provide electrical connectivity where needed while eliminating the need to cut through continuous thick metal during singulation, thereby reducing saw blade wear and debris generation.
Solution Approach 2:
The metal layer is applied with different properties in different locations: thick continuous metal over active die areas for low vertical resistance, and thin or absent metal over saw street areas for easy cutting. This local differentiation resolves the contradiction by providing the required electrical performance only where needed while facilitating easy singulation in other areas.
2Reliability
If the semiconductor die is made thinner to reduce vertical resistance, then the vertical resistance decreases, but the structural integrity of the die deteriorates
Solution Approach 1:
The semiconductor structure employs a composite approach combining ultra-thin semiconductor material with strategically placed metal regions and honeycomb support structures. The thin semiconductor layer provides low vertical resistance, while the metal and honeycomb structures provide the necessary mechanical support, allowing the die to be ultra-thin without sacrificing structural integrity.
Solution Approach 2:
The honeycomb pattern creates a porous-like support structure that provides mechanical strength while minimizing material usage. This allows the semiconductor die to be made ultra-thin for low vertical resistance while the honeycomb structure maintains structural integrity through its geometric design rather than relying on thick continuous material.
3Ease of manufacture
If backside openings are formed to enable lift-off of backside metal, then the manufacturing complexity increases, but the ability to singulate without cutting through thick metal improves
Solution Approach 1:
The backside openings are formed preliminarily before metal deposition, and the metal layer is designed to be self-aligned with these openings. This preliminary structuring of the substrate enables subsequent lift-off processing to automatically define the metal pattern, reducing the need for additional lithography and etching steps that would otherwise be required to create the segmented metal structure.
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 enables the production of ultra-thin semiconductor die with reduced vertical resistance and improved structural integrity, allowing for efficient singulation without damaging the saw blade and maintaining low on-resistance.
Implementation Method 1
A process involving the formation of backside openings and a honeycomb pattern of base substrate material to create ultra-thin semiconductor die, allowing for the lift-off of backside metal without cutting through thick metal layers
Implementation Method 2
using techniques like isotropic etching and plasma etching to achieve precision and structural support
Implementation Method 3
using techniques like isotropic etching and plasma etching to achieve precision and structural support
Data Source
AI summary
A semiconductor substrate contains a plurality of openings extending partially into a surface of the semiconductor substrate. A conductive layer is formed with a first portion of the conductive layer over a remaining portion of the surface of the semiconductor substrate between the openings and a second portion of the conductive layer in the openings. The remaining portion of the surface of the semiconductor substrate is removed to lift-off the first portion of the conductive layer while leaving the second portion of the conductive layer in the openings. The semiconductor substrate is singulated to separate the semiconductor die leaving the second portion of the conductive layer over a surface of the semiconductor die. Alternatively, a plurality of openings is formed over each semiconductor die. A conductive layer is formed over a remaining portion of the surface of the semiconductor substrate between the openings and into the openings.