[labnetwork] Chamber Cleaning With Gold Contamination

[Bob Henderson]

Kamal:

 

Cleaning a chamber that has been subjected to gold deposition is problematic. Gold as you probably know has no volatile byproducts with which to etch or clean it away after it adheres to a chamber sidewall or even shielding. The re-deposition of gold that is already within your chamber can occur when subjected to ion bombardment from subsequent depositions using various plasma sources like RF or magnetron deposition. This is why when making CMOS circuits even a small amount of gold deposited at the wrong process step like polysilicon deposition on top of gate oxide can cause substantial changes to the resistivity of the gate oxide which is the on/off switch for the transistor within the circuit. Most fabs have strict rules regarding gold in their fabrication areas. As for cleaning you could replace all of your shielding and cover any exposed gold pads with aluminum foil or Kapton tape if temperature is not going to be a problem and hope for the best results. We typically dedicate a chamber to gold use only after it has been used once. Better to separate by process than to have dead circuits at the end of your fabrication. Bob Henderson

 

From: labnetwork-bounces at mtl.mit.edu [mailto:labnetwork-bounces at mtl.mit.edu] On Behalf Of Kamal Yadav
Sent: Friday, June 05, 2015 2:33 AM
To: labnetwork at mtl.mit.edu
Subject: [labnetwork] Chamber Cleaning With Gold Contamination

 

Dear All,

 

Though may not make much sense, but would wanted to know if there are any successful cleaning procedures for chamber to remove affect of gold usage/contamination in that chamber.

 

We want to use the chamber with gold pads exposed to the plasma, but at the same time, need to allow those whose devices may get affected from gold [in CMOS]. Any intermediate cleaning/deposition that could significantly (?) reduce the affect. 

 

Our chamber [ICPCVD] has been used [5+ years] with gold pads [exposed to plasma] and so far other groups have not reported any issues with their devices, so its working out fine till now.

 

But we want to take precautionary measures if any.

 

Thanks a lot!

 

-- 

Thanks,

Kamal Yadav

Sr. Process Technologist

Electrical Engineering

IIT Bombay

Mobile: 7506144798

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