Protective Layer for TSV Tips During Thermo-Compression Bonding
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Solution Overview
Problem
During thermo-compression bonding of thin TSV die or wafers with protruding TSV tips, the irregular bottomside topography and non-uniform pressure distribution lead to issues such as pick-up damage, warpage, and cracking of the dielectric sleeve, resulting in poor bond integrity and yield.
Innovation Solution
A protective layer is applied over the protruding TSV tips on the bottomside of the TSV die to create a planar surface, reducing pressure concentration and distributing pressure more uniformly during bonding, thereby preventing damage and enhancing bond quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If TSV tips are left protruding for bonding, then bonding functionality is enabled, but pressure distribution becomes non-uniform causing warpage and damage
Solution Approach 1:
A protective layer is applied over the protruding TSV tips to act as an intermediary between the bonding pressure source and the TSV tips. This protective layer has a higher modulus than the dielectric sleeve and distributes the bonding pressure more uniformly across the TSV tip array, preventing warpage and damage while still enabling bonding functionality.
Solution Approach 2:
The protective layer changes the mechanical parameters at the TSV tip surface by providing a stiffer protective covering (higher modulus material). This parameter change allows the TSV tips to withstand bonding pressures more uniformly without deforming the underlying dielectric sleeve or causing warpage.
2Reliability
If pressure is applied during thermo-compression bonding, then bonding is achieved, but non-uniform pressure causes warpage and damage to thin TSV die
Solution Approach 1:
The protective layer is applied beforehand to cushion and distribute the bonding pressure uniformly across the TSV tips. This prevents concentration of stress that would otherwise cause warpage, cracking of the dielectric sleeve, or damage to the TSV tips themselves during the bonding process.
Solution Approach 2:
By introducing a protective layer with higher modulus than the dielectric sleeve, the mechanical strength parameter at the TSV tip surface is enhanced. This allows the thin TSV die to withstand bonding pressures without compromising structural integrity.
3Ease of operation
If TSV tips protrude significantly, then bonding contact is improved, but irregular topography causes non-uniform pressure distribution
Solution Approach 1:
The protective layer serves as an intermediary that covers the irregular topography of protruding TSV tips. It provides a more uniform surface that distributes bonding pressure evenly while still maintaining adequate contact for bonding functionality.
Solution Approach 2:
The protective layer acts as a thin film that conforms to the underlying TSV tip structure while providing a more uniform upper surface. This flexible covering maintains bonding contact while smoothing out the irregular topography that would otherwise cause non-uniform pressure distribution.
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 protective layer significantly reduces damage to TSV tips, eliminates non-uniform pressure-induced warpage, and enhances bond yield by ensuring more uniform pressure distribution, leading to improved co-planarity and reduced failures in the bonded devices.
Implementation Method 1
A protective layer is applied over the protruding TSV tips on the bottomside of the TSV die to create a planar surface, reducing pressure concentration and distributing pressure more uniformly during bonding
Implementation Method 2
Thermo-compression (TC) bonding is a common IC assembly method that involves the use of pressure (e.g., 40 to 80 N/cm2) applied by a bond head and a significant temperature (e.g., a temperature high enough to melt solder, such as 230 to 300° C.) to join two materials by interdiffusion across the boundary of the materials
Implementation Method 3
a temperature high enough to melt solder, such as 230 to 300° C.) to join two materials by interdiffusion
Implementation Method 4
The TSV tips may include a metal cap thereon, such as a cap including a nickel comprising layer, that can function as an inter-metallic compound (IMC) barrier to overlying Sn-based solder
Data Source
AI summary
A method of protecting through substrate via (TSV) die from bonding damage includes providing a substrate including a plurality of TSV die having a topside including active circuitry, a bottomside, and a plurality of TSVs that include an inner metal core that reaches from the topside to protruding TSV tips that extend out from the bottomside. A protective layer is formed on or applied to the bottomside of the TSV die including between and over the protruding TSV tips. The TSV die is bonded with its topside down onto a workpiece having a workpiece surface and its bottomside up and in contact with a bond head. The protective layer reduces damage from the bonding process including warpage of the TSV die by preventing the bond head from making direct contact to the protruding TSV tips.