Semiconductor Wire Bonding Stress Reduction via Ultrasonic Vibration
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Solution Overview
Problem
The existing wire bonding methods for connecting a metal wire to a semiconductor chip's electrode pad often apply significant stress, which can damage the pad and surrounding components, leading to reliability issues and potential electrical failures.
Innovation Solution
A modified wire bonding process that uses a combination of controlled load application, scrubbing operations, and ultrasonic vibration to uniformly activate the bonding interface, reducing stress concentrations and improving bonding strength while preventing damage to the pad and underlying layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ball portion is pressure-bonded onto the electrode pad using conventional ball bonding method, then electrical connection between wire and pad is achieved, but stress is applied to the electrode pad and surrounding members causing potential damage and reliability issues
Solution Approach 1:
The patent applies ultrasonic vibration to the ball portion during the bonding process. The vibration is applied in a specific direction (scrambling direction) that is different from the bonding direction, causing the ball portion to scramble and uniformly activate the bonding interface. This reduces stress concentration on the electrode pad and surrounding members while achieving reliable bonding.
Solution Approach 2:
The patent changes the parameters of the bonding process by applying ultrasonic vibration with specific frequency and amplitude, and by controlling the load application in combination with the vibration. This allows the bonding to proceed with reduced peak stress on the pad while maintaining bonding strength through the enhanced interface activation.
2Strength
If higher load is applied during ball bonding to ensure strong connection, then bonding strength is improved, but damage risk to the electrode pad and underlying layers increases
Solution Approach 1:
Ultrasonic vibration is applied to the ball portion during bonding, which enhances the bonding strength through increased interface activation and material softening. This allows achieving strong bonding with lower peak loads, thereby reducing the damage risk to the electrode pad and underlying layers.
Solution Approach 2:
The patent modifies the bonding parameters by introducing ultrasonic vibration frequency and amplitude as additional control variables. This enables the bonding process to achieve high bonding strength through the combined effect of vibration-enhanced diffusion and controlled load application, rather than relying solely on high mechanical load.
3Strength
If ultrasonic vibration is applied to activate bonding interface, then bonding strength is enhanced, but additional complexity is introduced to the bonding process
Solution Approach 1:
The bonding tool is designed to perform multiple functions: applying load, applying ultrasonic vibration, and controlling the vibration direction. By integrating these functions into a single tool, the patent avoids the need for separate equipment for each function, thereby reducing overall system complexity while achieving enhanced bonding strength.
Solution Approach 2:
The ultrasonic vibration is applied in a periodic manner with specific duty cycles and timing sequences. The vibration is activated only during critical bonding phases and deactivated when not needed, which simplifies control logic and reduces operational complexity compared to continuous vibration or multiple separate 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
The process effectively reduces stress on the electrode pad, enhances bonding reliability, and stabilizes electrical characteristics by forming a uniform alloy layer between the wire and pad, thereby improving the overall reliability of the semiconductor device.
Implementation Method 1
a period during which an ultrasonic wave is applied to the ball portion
Implementation Method 2
a period during which the bonding tool is pressed against the ball portion to apply a load
Data Source
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AI summary
As one embodiment, a method of manufacturing a semiconductor device, the method comprising the steps of: (a) preparing a semiconductor chip having an insulating film, and a first main surface in which a plurality of electrodes respectively exposed in a plurality of openings formed in the insulating film are formed; (b) preparing a base material including a second main surface over which the semiconductor chip is mounted, and a plurality of terminals; (c) after the step (a) and the step (b), mounting the semiconductor chip over the second main surface of the base material; (d) after the step (c), electrically connecting the plurality of electrodes and the plurality of terminals via a plurality of wires, respectively; and (e) after the step (d), resin-sealing the semiconductor chip and the plurality of wires, wherein in that , in the step (a), each of the plurality of electrodes of the semiconductor chip includes a first electrode having a first bonding surface exposed in a first opening among the plurality of openings, and in a plan view, each of the plurality of openings of the semiconductor chip has a plurality of sides including a first side extending in a first direction and a second side extending in a second direction intersecting the first direction, and wherein in that the step (d) includes the steps of: (ST2) bringing a ball portion of a first wire among the plurality of wires into contact with the first bonding surface of the first electrode ; (ST3) after the step (ST2), pressing the ball portion of the first wire toward the first bonding surface with a first load; (ST4) after the step (ST3), moving the ball portion of the first wire in a plurality of directions including two directions crossing each other in a plan view while pressing the ball portion against the first electrode with a second load smaller than the first load; (ST5) after the step (ST4), by applying a first ultrasonic wave having a first frequency to the ball portion of the first wire while pressing the ball portion against the first electrode with a third load equal to the second load or smaller than the second load, making the ball portion reciprocate along a third direction in a plan view; and (ST6) after the step (ST5), by applying the first ultrasonic wave having the first frequency while pressing the ball portion of the first wire against the first electrode with a fourth load larger than the third load and smaller than the first load, making the ball portion reciprocate along the third direction in a plan view, thereby bonding the ball portion and the first electrode.