Copper Sulfide Vias for Thermal Stability
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Solution Overview
Problem
The existing methods for forming through-wafer interconnects in microelectronic imagers, such as those used in digital cameras and cell phones, face issues with electrical continuity disruption due to solder deformation and high-temperature processes, which increase costs and thermal budget usage.
Innovation Solution
The formation of conductive vias in microfeature workpieces is achieved through chemically reactive processes, specifically using sulfur hexafluoride to react with copper layers and form copper sulfide, eliminating the need for solder and high-temperature vent holes, thereby ensuring stable and continuous electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solder is used to fill blind vias for forming through-wafer interconnects, then electrical connections can be established, but the solder may deform or melt during reflow processes, disrupting electrical continuity
Solution Approach 1:
The patent changes the material parameter from solder to copper sulfide, which has a significantly higher melting point and thermal stability. This parameter change eliminates the deformation and melting issues that occur with solder during reflow processes, thereby maintaining electrical continuity and improving reliability.
Solution Approach 2:
The patent replaces the reusable but thermally vulnerable solder with copper sulfide, which is thermally stable and can withstand multiple reflow cycles without degradation. This substitution makes the interconnect structure more robust for repeated thermal processing.
2Ease of manufacture
If vent holes are formed and high-temperature processes are used to fill vias with solder, then via filling can be achieved, but the number of steps and thermal budget increase production costs
Solution Approach 1:
The patent extracts and eliminates the vent hole formation step from the manufacturing process. By using copper sulfide instead of solder, the process no longer requires vent holes to allow gas escape during filling, thereby reducing the number of manufacturing steps and simplifying the overall process.
Solution Approach 2:
The patent replaces the mechanical/thermal process of solder filling (which requires vent holes and high temperatures) with a chemical deposition process forming copper sulfide. This substitution eliminates the need for complex venting mechanisms and high-temperature processing, reducing device complexity.
3Ease of manufacture
If high-temperature processes are used to fill vias with solder, then via filling can be achieved, but a significant portion of the thermal budget is consumed
Solution Approach 1:
The patent changes the processing temperature parameter from high-temperature solder reflow to lower-temperature copper sulfide formation. This parameter change significantly reduces thermal budget consumption while still achieving complete via filling and maintaining electrical connectivity.
Solution Approach 2:
The patent replaces the thermal-based solder filling process with a chemical-based copper sulfide formation process. This substitution reduces reliance on high-temperature thermal energy, thereby conserving the thermal budget for other critical processing 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 approach reduces the risk of electrical discontinuity, decreases production costs, and conserves thermal budget by using lower temperature chemical reactions to form robust and continuous conductive interconnects, which are less prone to deformation and oxidation.
Implementation Method 1
chemically reactive processes, specifically using sulfur hexafluoride to react with copper layers and form copper sulfide
Data Source
AI summary
Microfeature workpieces having conductive vias formed by chemically reactive processes, and associated systems and methods are disclosed. A method in accordance with one embodiment includes disposing a conductive lining on walls of a via in a microfeature workpiece, so that a space is located between opposing portions of the lining facing toward each other from opposing portions of the wall. The method can further include chemically reacting the lining with a reactive material to form a chemical compound from a constituent of the reactive material and a constituent of the lining. The method can still further include at least partially filling the space with the compound. In particular embodiments, the conductive lining includes copper, the reactive material includes sulfur hexafluoride, and the chemical compound that at least partially fills the space in the via includes copper sulfide.