Top Conductive Pad Etching Using C4F8/O2/Ar Plasma
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Solution Overview
Problem
The existing methods for forming top conductive pads in semiconductor devices using SF6 plasma lead to defects such as over-etching and fluorination, which result in oxide and fluoride residues that negatively affect wire bonding and electrical connections, causing loss of the conductive pad and reducing its bondability and conductivity.
Innovation Solution
A method involving the use of a plasma containing a partially or fully fluorinated hydrocarbon without SF6 is employed to pattern and etch the anti-reflective coatings and passivation films, ensuring the top conductive pad remains free of oxide and fluoride, thereby preventing fluorination and maintaining high electrical conductivity and bondability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If SF6 plasma is used to etch anti-reflective coatings and passivation films, then the etching process is effective, but the top conductive pad becomes fluorinated and forms oxide/fluoride residues that reduce bondability and conductivity
Solution Approach 1:
The patent changes the chemical composition parameters of the plasma etching process by replacing SF6 plasma with a mixed gas plasma containing C4F8 (octafluorocyclobutane), O2 (oxygen), and Ar (argon) in specific ratios. This parameter change allows the etching process to remain effective while preventing fluorination of the aluminum pad, thereby maintaining bondability and conductivity without sacrificing etching efficiency
Solution Approach 2:
The patent uses a composite plasma environment combining multiple gases (C4F8, O2, Ar) rather than a single gas. The C4F8 provides etching capability, O2 prevents oxide formation and removes fluorine residues, and Ar serves as a buffer gas. This composite approach achieves both effective etching and protection of the conductive pad properties
2Manufacturing precision
If SF6 plasma etching is used, then the anti-reflective coating and passivation film are effectively removed, but the top conductive pad loses material and suffers from fluoride contamination
Solution Approach 1:
The patent modifies the plasma chemistry parameters by introducing O2 into the etching gas mixture. The oxygen component reacts with fluorine species to form volatile CF4 and COF2, preventing fluoride deposition on the aluminum pad. This parameter change reduces material loss and eliminates fluoride contamination while preserving the precision of the etched pattern
Solution Approach 2:
The patent introduces oxygen as an intermediary substance that mediates between the etching process and the aluminum pad. The oxygen acts as a protective intermediary that reacts with fluorine radicals to prevent them from attacking the aluminum, thereby reducing material loss and preventing contamination during the pattern formation process
3Productivity
If traditional SF6 plasma process is used, then the etching rate is sufficient, but oxide and fluoride residues remain on the pad surface affecting electrical properties
Solution Approach 1:
The patent employs a composite plasma environment combining C4F8, O2, and Ar gases. The C4F8 maintains high etching rate, while the O2 component continuously cleans the pad surface by reacting with fluorine to form volatile compounds. This composite approach simultaneously achieves high etching rate and excellent surface cleanliness with improved electrical properties
Solution Approach 2:
The patent implements a continuous dual-function plasma process where C4F8 continuously provides etching action while O2 simultaneously performs surface cleaning. This continuous dual action ensures that the etching rate is maintained while fluoride residues are continuously removed, achieving both high productivity and high manufacturing precision
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
This approach significantly reduces the loss of the top conductive pad during etching and fluorination, improves manufacturing efficiency, and enhances the bondability and conductivity of the pad, with experiments showing a loss reduction from greater than 5% to less than 2.9% and an increase in wafer etching rate by 9-15% compared to traditional methods.
Implementation Method 1
A method involving the use of a plasma containing a partially or fully fluorinated hydrocarbon without SF6 is employed to pattern and etch the anti-reflective coatings and passivation films
Data Source
AI summary
A method for making a semiconductor device is disclosed. A substrate comprising semiconductor device elements is provided. A top conductive pad and an anti-reflective coating are patterned over the substrate. The anti-reflective coating is disposed on the top conductive pad. At least one passivation film is formed over the substrate and the anti-reflective coating. The at least one passivation film and the anti-reflective coating are etched to form a trench therein so as to expose a portion of the top conductive pad.