Backside Standoff Structures for Semiconductor Devices
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Solution Overview
Problem
Existing semiconductor device manufacturing processes face challenges in achieving small size and lead-free soldering without using Pb, while maintaining reliable electrical and thermal connections and preventing issues like die warp, cracking, and intermetallic fracture planes.
Innovation Solution
The implementation of Cu or Ni standoff structures embedded within a Sn-containing layer on the backside of semiconductor devices, which are isolated and configured to mirror leadframe indentations, allowing for Pb-free soldering and improved thermal and electrical conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Pb-free soldering is implemented, then environmental compliance and device miniaturization are improved, but soldering reliability and resistance to intermetallic fracture deteriorate
Solution Approach 1:
A Ni or Cu intermediary layer is introduced between the Pb-free solder and the die backmetal layer. This intermediary layer acts as a buffer that reduces stress concentration and prevents direct formation of brittle intermetallic compounds between the solder and substrate, thereby maintaining soldering reliability while enabling Pb-free processing
Solution Approach 2:
The thickness of the Ni or Cu stand-off structures is controlled within specific ranges (0.5-5.0 micrometers) to optimize the balance between preventing intermetallic fracture and maintaining electrical/thermal conductivity. This parameter optimization resolves the contradiction by finding the ideal thickness that provides both mechanical protection and functional performance
2Volume of moving object
If die size is reduced, then device miniaturization is improved, but thermal and electrical conductivity deteriorate
Solution Approach 1:
The backside metallization structure uses a composite configuration combining Ni or Cu stand-off structures with Pb-free solder material. The Ni/Cu portions provide high electrical and thermal conductivity pathways, while the solder provides mechanical bonding, achieving both miniaturization and maintained conductivity in the reduced die size
Solution Approach 2:
Instead of relying on large planar contact areas for conductivity, the invention uses vertically oriented Ni or Cu stand-off structures that extend through the solder layer. This three-dimensional approach maintains conductivity pathways in the vertical dimension, compensating for the reduced horizontal die size
3Reliability
If Ni or Cu stand-off structures are used, then electrical and thermal conductivity are improved, but manufacturing complexity increases
Solution Approach 1:
The formation of Ni or Cu stand-off structures is merged with the existing backside metallization process sequence. The stand-off structures are deposited and patterned as integrated steps within the overall device fabrication flow, combining multiple functions (conductive pathway creation, mechanical support, and stress management) into a unified manufacturing process rather than adding separate complex 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 solution enables the production of smaller semiconductor devices with enhanced reliability and reduced risk of cracking and intermetallic fracture, while providing improved thermal and electrical conductivity, and eliminating the need for Pb in soldering processes.
Implementation Method 1
improved thermal and electrical conductivity
Implementation Method 2
improved thermal and electrical conductivity
Data Source
AI summary
Standoff structures that can be used on the die backside of semiconductor devices and methods for making the same are described. The devices contain a silicon substrate with an integrated circuit on the front side of the substrate and a backmetal layer on the backside of the substrate. Standoff structures made of Cu of Ni are formed on the backmetal layer and are embedded in a Sn-containing layer that covers the backmetal layer and the standoff structures. The standoff structures can be isolated from each other so that they are not connected and can also be configured to substantially mirror indentations in the leadframe that is attached to the Sn-containing layer. Other embodiments are described.