Wire Bond Alignment Sensing Structures for Semiconductor Die
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Solution Overview
Problem
Wire bonding misalignment in semiconductor assemblies can lead to latent shorts that are not detectable during assembly, resulting in device failures during burn-in or in the field, as existing inspection methods are not compatible with mass production and struggle to detect misaligned bond wires, especially with small bond pad pitches.
Innovation Solution
Incorporating wire bond alignment sensing structures on semiconductor die, which include a guard element spaced closer than the minimum gap between bond pads, enhancing sensitivity to misalignment and allowing for detection of latent shorts during final testing without additional contacts or probes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional bond pads with minimum spacing are used, then manufacturing precision is maintained, but measurement precision of wire bond misalignment deteriorates
Solution Approach 1:
The bond pad structure is segmented into two functional parts: the conventional bond pad for wire bonding and the guard ring structure for alignment sensing. The guard ring is spaced closer to the bond pad than minimum spacing rules require, creating a dedicated sensing zone that enhances misalignment detection capability without affecting the electrical bonding function.
Solution Approach 2:
The guard ring acts as an intermediary element between the bond pad and adjacent structures. It serves as a sensing structure that detects wire bond misalignment through electrical continuity testing, while maintaining the minimum spacing requirements for the actual bond pads. The guard ring translates physical misalignment into detectable electrical signals.
2Measurement precision
If microscope inspection is performed to detect misaligned wire bonds, then measurement precision improves, but productivity deteriorates
Solution Approach 1:
The mechanical/optical inspection system (microscope) is replaced with an electrical sensing system. The guard ring structure enables automated electrical continuity testing that can be integrated into existing wire bond testing equipment, eliminating the need for manual or automated optical microscopy while maintaining detection capability.
Solution Approach 2:
The guard ring structure enables the bond pad assembly to self-test for misalignment through electrical continuity measurements. The sensing structure is inherently part of the bond pad structure, allowing the system to detect its own alignment status without requiring external inspection equipment or additional testing steps.
3Productivity
If final electrical test is performed after burn-in, then productivity is maintained, but measurement precision of latent shorts deteriorates
Solution Approach 1:
The guard ring sensing structure enables alignment verification to be performed as a preliminary test during the wire bonding process itself, before burn-in stress is applied. By detecting misalignment early through electrical continuity testing of the guard ring, potential latent shorts are identified before they can develop into actual failures during burn-in or field operation.
Data Source
AI summary
A semiconductor die includes a substrate having a topside including active circuitry having an array of bond pads thereon separated by gaps including a minimum gap. At least a portion of the array of bond pads are connected to nodes in the active circuitry. At least one wire bond alignment sensing structure includes a first bond pad selected from the array of bond pads, and a guard element positioned along at least a portion of the first bond pad. The guard element is spaced apart by a distance shorter than the minimum gap from the first bond pad.