Non-Contact TSV Joint Integrity Testing via Voltage Contrast
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Solution Overview
Problem
There is a lack of practical solutions to test the joint integrity between TSV die and package substrates in partially assembled stacks, especially since standard contact probing methods can damage the protruding TSV tips, leading to unreliable joints and reduced bond yield.
Innovation Solution
A non-contact voltage contrast method using a charged particle beam to generate secondary electron emissions, allowing for the determination of TSV continuity and joint integrity without electrical access to the TSV die, utilizing a reference beam for precharging and a primary beam for rastering to enhance signal contrast and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standard contact probe techniques are used to test TSV die contacts, then electrical joint integrity can be evaluated, but the protruding TSV tips are damaged leading to unreliable joints and reduced bond yield
Solution Approach 1:
The patent replaces the mechanical contact probe system with a non-contact charged particle beam system. Instead of using physical probes that touch and potentially damage the TSV tips, the invention uses a charged particle beam (electrons, protons, or ions) to generate secondary electron emissions for voltage contrast imaging, enabling electrical testing without mechanical contact and thus avoiding damage to the protruding TSV tips
Solution Approach 2:
The patent introduces secondary electron emissions as an intermediary mechanism to transfer electrical information from the TSV die to the detector. The charged particle beam excites secondary electron emissions from the TSV contacts, and these secondary electrons carry the voltage contrast information that indicates joint integrity, allowing indirect electrical testing without direct contact
2Strength
If the carrier wafer is present during assembly, then mechanical support is provided, but electrical access to one side of the TSV die is blocked making testing difficult
Solution Approach 1:
The charged particle beam acts as an intermediary that can penetrate or work around the carrier wafer obstruction. By generating secondary electron emissions from the TSV contacts through the beam, the system可以获得 electrical information about joint integrity without requiring direct electrical access that would be blocked by the carrier wafer
Solution Approach 2:
The patent transitions from in-plane electrical access (which is blocked by the carrier wafer) to out-of-plane detection using charged particle beam and secondary electron emissions. This dimensional change allows the testing system to access electrical information from the top surface of the TSV die without being obstructed by the carrier wafer underneath
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
Enables reliable non-contact evaluation of TSV joint integrity, reducing damage to TSV tips and improving bond yield by providing a method to detect high resistance or open joints, even in electrically floating IC stacks.
Implementation Method 1
utilize at least one charged particle beam to generate secondary electron emissions
Data Source
AI summary
A non-contact voltage contrast (VC) method of determining TSV joint integrity after partial assembly. A TSV die is provided including TSVs that extend from a frontside of the TSV die to TSV tips on a bottomside of the TSV die. At least some TSVs (contacting TSVs) are attached to pads on a top surface of a multilayer (ML) package substrate. The ML package substrate is on a substrate carrier that blocks electrical access to the frontside of the TSV die. Two or more nets including groups of contacting TSVs are tied common within the ML substrate. A charged particle reference beam is directed to a selected TSV within a first net and a charged particle primary beam is then rastered across the TSVs in the first net. VC signals emitted are detected, and joint integrity for the contacting TSVs to pads of the ML package substrate is determined from the VC signals.