Aluminum Alloy Bond Pads for Probing Reliability
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Solution Overview
Problem
The reliability of wire bonding on aluminum bond pads is compromised due to mechanical deformation and cracking caused by high contact forces during wafer testing, leading to yield losses and early failures, especially in high-power devices that require repeated probing at different temperatures.
Innovation Solution
The use of aluminum alloys with specific compositions, such as AlZnMgCu, AlCuTiMgAg, AlCuZr, AlSc, AlMgZr, AlSiZr, and AlMgSi, which provide enhanced mechanical properties like increased hardness and tensile strength, reducing the likelihood of bond pad deformation and cracking during probing and wire bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high contact forces are applied during wafer probing to ensure sufficient electrical contact, then electrical contact reliability is improved, but mechanical deformation and cracking of the bond pad and underlying oxide layer occur
Solution Approach 1:
The patent changes the material parameters of the bond pad by introducing specific alloying elements (Zn, Mg, Sc, Zr, Ti, Ag, Mn) in controlled amounts (at least 0.3% by weight of each). This modifies the mechanical properties of aluminum, increasing its hardness and strength to resist probing-induced deformation while maintaining electrical conductivity for reliable contact
Solution Approach 2:
The patent creates a composite aluminum alloy material by combining aluminum with multiple alloying elements (Zn, Mg, Sc, Zr, Ti, Ag, Mn, and optionally Cu and Si). This composite structure provides both the electrical conductivity of aluminum and the enhanced mechanical strength needed to withstand probing forces without deformation or cracking
2Adaptability or versatility
If repeated wafer probing is performed at different temperatures for high power device testing, then device characterization capability is improved, but the risk of mechanical damage to bond pads and underlying layers increases
Solution Approach 1:
The patent modifies the thermal and mechanical parameters of the bond pad material through alloying. The added elements change the material's thermal expansion characteristics and mechanical strength, enabling it to withstand repeated thermal cycling and probing at different temperatures without accumulating damage
Solution Approach 2:
The patent applies beforehand cushioning by pre-hardening the bond pad through alloying before the repeated probing and thermal cycling begins. The alloying elements create a more resilient material structure that can absorb and distribute mechanical and thermal stresses, preventing cumulative damage during subsequent testing operations
Data Source
AI summary
A semiconductor substrate has a bond pad. The bond pad includes a layer of an aluminum alloy having a chemical composition including at least 0.3% by weight of at least one of Zn, Mg, Sc, Zr, Ti, Ag and/or Mn, with the balance being at least Al and incidental impurities.