Electrode Array Height Gradient for Wafer Bonding Stress
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Solution Overview
Problem
In stacked semiconductor devices, the high load required for bonding electrodes can damage the electrodes or the wafer, especially due to uneven stress distribution in two-dimensional arrays, where peripheral electrodes lack load sharing and are prone to excessive stress during bonding.
Innovation Solution
A substrate design featuring a base with a two-dimensional electrode array that includes a central portion and an incremental region around it, where electrode heights gradually increase towards the center, along with dummy electrodes not connected to the wiring, helps distribute stress more evenly during bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If electrodes are formed as a two-dimensional array in a region having a predetermined area, then the number of electrodes can be increased to achieve high functionality, but the stress concentration on peripheral electrodes increases and may cause damage
Solution Approach 1:
The patent applies local quality by creating different electrode height levels in different regions of the electrode array. Specifically, peripheral electrodes are positioned at a first height level while central electrodes are positioned at a second height level, with intermediate electrodes at intermediate height levels. This local differentiation allows peripheral electrodes to bear less stress during bonding while maintaining the overall high electrode count for functionality.
Solution Approach 2:
The electrode array is segmented into multiple height levels or tiers based on position. The segmentation divides the uniform two-dimensional array into peripheral regions (first height level), intermediate regions (intermediate height levels), and central regions (second height level). This segmentation enables differential stress distribution across the array, protecting peripheral electrodes while maintaining electrical connectivity.
2Reliability
If a high load is applied to wafers for bonding electrodes, then electrical connection between electrodes can be achieved, but the electrodes or wafer may be damaged due to the high load
Solution Approach 1:
The patent changes the geometric parameter of electrode height to optimize stress distribution. By setting peripheral electrodes at a lower first height level and central electrodes at a higher second height level, the bonding load is distributed more favorably. This parameter change allows reliable electrical connection to be achieved while reducing the peak stress on any single electrode or wafer region, thereby preventing damage.
3Area of stationary object
If electrodes in the peripheral portion are present without other electrodes around them, then the electrode array can be formed with a predetermined area, but the load cannot be shared in that region leading to excessive stress
Solution Approach 1:
The patent adds a vertical dimension (height level) to the traditional two-dimensional electrode array. By positioning peripheral electrodes at a first height level and central electrodes at a second height level, the invention creates a three-dimensional electrode structure. This dimensional change enables load sharing through the vertical hierarchy, where intermediate electrodes at intermediate height levels can distribute bonding forces, allowing the peripheral electrodes to be part of a larger area array without suffering from unshared load.
Data Source
AI summary
A substrate includes a base member having a predetermined thickness, and an electrode array provided in one surface in a thickness direction of the base member and having a plurality of electrodes arranged two-dimensionally in a plan view, and the electrode array includes a central portion and an incremental region provided around the central portion in the planar view and is formed so that a height of the electrodes in the incremental region gradually increase as approaching toward the central portion.