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Using high aspect ratio probes

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Burden posted on Wed, Nov 10 2010 11:48 AM

I am attempting to image a deep hole in glass (>20 microns deep, 2 microns diameter).  I have been using Scanassyst probes (both air and fluid) in Peak Force Tapping mode with a Catalyst system.  However, I am about to begin a trial with high aspect ratio probes (specifically, TESP-HAR) to help better define the hole edges.

Since this tip is not coaed with Al, how cautious should I be using the Scanassyst mode with the TESP-HAR?  Is peak force tapping mode a bad idea with this tip?  If not, would it be better to operate manually (rather than in Scanassyst mode) to ensure tip protection?  Or, should I really be seeking to use the metal-coated TESPA-HAR for Peak Force Tapping mode?

The TESP-HAR also has a significantly higher force constant the the Scanassyst tips we've been using (42N/m vs. ~1N/m).  How might this affect the settings I choose?

Any advise that could be passed along would be greatly appreciated.

Thanks.

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Verified by Burden

Hello Dan,

You should be able to use peak force mode with TESP-HAR probes, although as you point out, they do have high spring constant (40N/m nominally).  This would apply higher force to the tip - if you are not imaging high resolution features <10nm, it shouldn't be problem.  The High aspect ratio should get you better profile of the trench wall.

For best control of everything, I would suggest trying first with manual control of the force setpoint.  You can set the ScanAsyst to "Independent" and then allow the scanasyst to automatically optimize the gain, but give you control of the setpoint.  Before engaging, put in nominal values for spring constant and deflection sensitivity (or you can measure on a hard sample) to get a sense as to the force you are applying.  Engage with scan size of 0nm and verify that the force curve on the surface looks reasonable before beginning scanning. 

It should work either with TESP-HAR or with TESPA-HAR.  If possible, try both and see which gives better performance with your particular experimental setup. 

Best of luck!

Adam

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Verified by Burden

Additionally, you might want to try dropping the "Engage setpoint" to 0.08V (in the "Other" controls in scan parameter list) and the engage step size to 0.5um (in the general engage parameters).  This will help give a softer engage when using stiffer probes with Peak Force Tapping, but you might have problems with false engaging if you make the Engage setpoint too small.

Obviously, you will probably not reach the bottom of the pit since the Z scan range of your scanner is ~20 um, but you should still be able to get a good idea of the position of the edges.

Let us know how it goes...

--Bede

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Top 50 Contributor
17 Posts
Points 143
Verified by Burden

Hello Dan,

You should be able to use peak force mode with TESP-HAR probes, although as you point out, they do have high spring constant (40N/m nominally).  This would apply higher force to the tip - if you are not imaging high resolution features <10nm, it shouldn't be problem.  The High aspect ratio should get you better profile of the trench wall.

For best control of everything, I would suggest trying first with manual control of the force setpoint.  You can set the ScanAsyst to "Independent" and then allow the scanasyst to automatically optimize the gain, but give you control of the setpoint.  Before engaging, put in nominal values for spring constant and deflection sensitivity (or you can measure on a hard sample) to get a sense as to the force you are applying.  Engage with scan size of 0nm and verify that the force curve on the surface looks reasonable before beginning scanning. 

It should work either with TESP-HAR or with TESPA-HAR.  If possible, try both and see which gives better performance with your particular experimental setup. 

Best of luck!

Adam

  • | Post Points: 13
Top 10 Contributor
280 Posts
Points 6,219
Bruker Employee
Verified by Burden

Additionally, you might want to try dropping the "Engage setpoint" to 0.08V (in the "Other" controls in scan parameter list) and the engage step size to 0.5um (in the general engage parameters).  This will help give a softer engage when using stiffer probes with Peak Force Tapping, but you might have problems with false engaging if you make the Engage setpoint too small.

Obviously, you will probably not reach the bottom of the pit since the Z scan range of your scanner is ~20 um, but you should still be able to get a good idea of the position of the edges.

Let us know how it goes...

--Bede

Top 500 Contributor
4 Posts
Points 44
Burden replied on Thu, Nov 11 2010 8:44 PM

Thanks Bede and Adam.  I'll be touch.

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