Plasma Treatment for Semiconductor Pad Surface Roughness Control
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Solution Overview
Problem
Plasma treatment before wire bonding in semiconductor devices adversely affects the bonding strength between the pad and the wire, leading to reduced reliability due to increased surface roughness and oxide film thickness on the pad.
Innovation Solution
Adjusting the plasma treatment conditions, such as reducing high-frequency power, increasing discharge pressure, and shortening processing time, to maintain surface roughness of the pad at 3.3 nm or less, thereby reducing oxide film thickness and enhancing bonding strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If plasma treatment is performed to clean the lead surface before wire bonding, then contamination is suppressed and bonding reliability is improved, but the bonding strength between the pad and wire is reduced due to increased surface roughness and oxide film thickness
Solution Approach 1:
The invention changes the parameters of plasma treatment (gas type, pressure, power, treatment time) to achieve the optimal balance between cleaning effectiveness and surface roughness control. Specifically, using CF4 gas at 0.5-5 Pa pressure with 10-100 W power for 1-30 seconds maintains surface roughness at 3.3 nm or less while still removing contamination, thereby preserving bonding strength without sacrificing cleaning effectiveness
2Reliability
If plasma treatment is performed with high power to ensure thorough cleaning, then contamination removal is improved, but surface roughness increases and bonding strength decreases
Solution Approach 1:
The invention optimizes plasma treatment parameters by using CF4 gas at low pressure (0.5-5 Pa) with moderate power (10-100 W) for short duration (1-30 seconds). This parameter combination achieves effective contamination removal while limiting surface roughness increase to 3.3 nm or less, preventing the trade-off between cleaning effectiveness and surface quality
3Strength
If plasma treatment conditions are optimized to reduce surface roughness, then bonding strength is maintained, but the cleaning effectiveness on the lead surface may be compromised
Solution Approach 1:
The invention uses CF4 plasma at 0.5-5 Pa pressure with 10-100 W power for 1-30 seconds, which simultaneously achieves both effective lead surface cleaning and controlled pad surface roughness (≤3.3 nm). This parameter optimization ensures that contamination is removed from the lead while the pad surface remains smooth enough for strong bonding, eliminating the need to compromise between these two requirements
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
Improves the bonding strength between the pad and the wire by ensuring direct contact and promoting alloying, while maintaining the original purpose of suppressing contamination effects on the inner lead.
Implementation Method 1
a surface treatment step of performing a plasma treatment (S102) on the semiconductor chip having the pad on the surface
Implementation Method 2
improves the bonding strength between the pad and the wire by ensuring direct contact and promoting alloying
Data Source
AI summary
The reliability of semiconductor device is improved. The method of manufacturing a semiconductor device has a step of performing plasma treatment prior to the wire bonding step, and the surface roughness of the pads after the plasma treatment step is equal to or less than 3.3 nm.