Under-Bond-Pad Sensor Circuit for Memory Die Stress Detection
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Solution Overview
Problem
Conventional techniques for detecting die stress during memory device assembly are inadequate, often relying on limited data and failing dies, leading to reduced yield, reliability issues, and marginal functionality, without effectively quantifying the impact of process variations.
Innovation Solution
Incorporating an active monitor, such as a sensor circuit with ring oscillators, under the conductive bonding pads of the die to assess stress and process variations during pre-package and post-package stages, allowing for early detection and correction of potential damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional detection techniques are used, then device complexity is reduced, but measurement precision and reliability are insufficient
Solution Approach 1:
The patent introduces sensor circuits as intermediary elements that indirectly measure stress through electrical parameter changes. These sensor circuits act as mediators between the physical stress on the die and the measurable electrical signals, enabling precise stress detection without requiring complex direct measurement apparatus.
Solution Approach 2:
The patent replaces mechanical stress measurement systems with electrical measurement systems. By using sensor circuits that convert mechanical stress into electrical signals (through resistance, capacitance, or frequency changes), the system achieves higher precision while reducing overall device complexity, as electrical measurements are inherently more precise and easier to integrate than mechanical ones.
2Productivity
If limited data from failing dies is used, then manufacturing cost is reduced, but productivity and yield are reduced
Solution Approach 1:
The patent implements preliminary stress assessment using sensor circuits before final packaging and testing. By detecting stress early in the manufacturing process, the system can identify and address potential failures before they become permanent, thereby improving yield without requiring extensive post-manufacturing testing and reducing the need to discard potentially good dies based on limited failure data.
3Reliability
If die stress is not detected early, then device complexity is reduced, but reliability deteriorates due to permanent damage
Solution Approach 1:
The patent implements a feedback mechanism where sensor circuits continuously monitor stress conditions and provide real-time data about die integrity. This feedback loop enables early warning of potential failures, allowing corrective actions to be taken before permanent damage occurs, thereby significantly improving reliability. The feedback system uses simple electrical measurements rather than complex monitoring apparatus, keeping device complexity manageable.
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
Enhances yield and reliability by enabling real-time stress detection and process improvement, reducing permanent damage and maintaining circuit functionality.
Implementation Method 1
The sensor circuit can be enabled during different stages (e.g., pre-package and post-package stage) of fabrication of the memory device to provide evaluation information. The collected evaluation information can also allow analysis on the impact of stress on the die during packaging assembly
Implementation Method 2
In an example, ring oscillators are included in the sensor circuit
Data Source
AI summary
Some embodiments include apparatuses and methods of fabricating the apparatuses. One of the apparatuses includes a substrate of a semiconductor die; a memory cell portion located over a first portion of the substrate; a conductive pad portion located over a second portion of the substrate and outside the memory cell portion; and a sensor circuit including a portion located over the second portion of the substrate and under the conductive pad portion. The conductive pad portion includes conductive pads. Each of the conductive pads is part of a respective electrical path coupled to a conductive contact of a base outside the substrate.