[labnetwork] Etch rate of expired BOE solution

[Mac Hathaway]

Hi Savitha,

I don't have personal experience with old BOE, but since HF is made by 
bubbling HF gas through water, I would expect the HF gas to come out of 
solution and evaporate over time, lowering the HF concentration.  If the 
bottles have been sealed, I don't know why it would weaken.

While adding fresh 49% HF to the existing stock would increase the etch 
rate, figuring out the concentration of your "resultant" mixture would 
be challenging, since you don't know the current (weakened) concentration.

If you are doing an etch where knowing the precise etch rate is 
important, you might try just doing a rate test on each bottle as it is 
opened and put into use, marking the rate on the side of the bottle, and 
letting that suffice.

I am unaware of any other issues that can arise from the use of old HF 
or BOE, such as surface roughening, or things like that.  Other more 
experienced hands will no doubt weigh in...


Mac

Mac Hathaway

Senior Process and Systems Engineer

Harvard Center for Nanoscale Systems

11 Oxford St.

Cambridge, MA02138

617-495-9012


On 10/9/2017 1:05 PM, Savitha P wrote:
>
> Hi all,
>
>
> We have a lot of BOE(13:2) solution expired in 2014, which has been 
> seeing declining oxide etch rates since sometime.  Is there some way 
> of improving the etch rate, like by adding fresh HF (50%).
>
>
> Kindly let me know if anyone has information on this.
>
>
> Regards,
>
>
> Savitha
>
> ________________________________
>
> Dr. Savitha P
> Chief Operating Officer
> National Nanofabrication Centre
> Centre for Nanoscience and Engineering
> Indian Institute of Science
> Bangalore - 560012
> India.
> Ph. +91 80 2293 3254
> www.cense.iisc.ac.in
> /**Please note the change in my e-mail id**/
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