Hydrogen Plasma Reduction of Copper Oxide Films on 300 mm Wafers
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Solution Overview
Problem
Current methods for removing metal oxide films from metals, such as copper, using atmospheric pressure argon and hydrogen plasma are too slow for commercial applications, requiring over 12 minutes to process 300 mm wafers at substrate temperatures below 200°C.
Innovation Solution
An atmospheric pressure plasma apparatus is designed to generate a high density of hydrogen radicals by feeding argon and hydrogen gases into a plasma device with RF power, allowing for the rapid removal of metal oxide layers from metals by scanning the plasma beam over the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If atmospheric pressure argon and hydrogen plasma is used to remove metal oxide films, then the metal oxide removal is effective, but the processing speed is too slow for commercial applications
Solution Approach 1:
The patent changes the plasma generation parameters by using radio frequency (RF) power at 27.12 MHz instead of conventional methods, and operates at atmospheric pressure with specific gas flow rates (15.0 LPM argon, 1.0 LPM forming gas) to achieve higher reactive species concentration and faster oxide removal rates
Solution Approach 2:
The patent employs periodic scanning motion of the plasma beam across the substrate surface, moving the plasma source back and forth in a controlled manner to achieve uniform oxide removal across the entire 300 mm wafer surface while maintaining high processing speed
2Productivity
If the plasma beam is scanned quickly over the substrate to increase throughput, then processing time is reduced, but uniformity of oxide removal may be compromised
Solution Approach 1:
The patent incorporates feedback control through a controller that monitors and adjusts the scanning speed, plasma power, and gas flow rates in real-time to maintain uniform oxide removal across the substrate, ensuring consistent processing quality at high throughput
Solution Approach 2:
The patent uses dynamic scanning motion with variable speeds across different regions of the substrate, adjusting the plasma beam trajectory and speed to compensate for edge effects and ensure uniform processing across the entire wafer surface
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 proposed solution significantly increases the throughput of metal oxide removal, capable of processing 300 mm wafers in several minutes or less at substrate temperatures below 200°C, while maintaining a uniform removal rate and avoiding particle deposition on the surface.
Implementation Method 1
A plasma consists of an ionized gas, containing free electrons, positive ions, and negative ions
Implementation Method 2
The free electrons in these gas discharges are accelerated to an extremely high velocity, exhibiting electron temperatures in the range of 1.0 to 3.0 electron volts (eV). These energetic electrons smash into molecules, such as oxygen (O2) or hydrogen (H2), and dissociate them into atoms, such as O or H.
Implementation Method 3
The atmospheric pressure argon (or helium) plasma is driven by a radio frequency (RF) power source at 27.12 MHz
Implementation Method 4
the metal oxide on the surface of the metal features is rapidly removed by the reaction, MOx(s)+2xH(g)=M(s)+xH2O(g)
Data Source
AI summary
Metal oxide films are reduced to metal with an atmospheric pressure argon and hydrogen plasma at temperatures between 25 and 250° C. A 40-nm-thick copper oxide layer on a copper-coated silicon wafer, 300 mm in diameter, can be fully removed by the argon and hydrogen plasma in under two minutes at 150° C. The fast rate of metal oxide reduction to metal demonstrates that this process is well suited for front- and back-end semiconductor manufacturing, such as for example, flux-free flip chip bonding of microbumps.