The Nanoscale World

Why ´Bias´ changes the slope of ´Potential´Scope in Surface Potential Detection?

rated by 0 users
Answered (Not Verified) This post has 0 verified answers | 10 Replies | 2 Followers

Top 25 Contributor
58 Posts
Points 652
stsolong posted on Wed, Jun 13 2012 9:51 AM

Dear friends, I have some problems concerning surface potential detection.  The most confusing one is the function of ´Bias´. The following statement is the details. I would be very grateful if you can leave your comments here.

Equipment: Dimension 3100. NanoScope4 controller;

Software: NanoScope V5.23

Sample: Si wafer as substrate,  less than 1 mm patterns (inside the patterns, there are inter-metallic compounds) on the surface . The sample is directly put on the sample chuck.

Normally, by varying the interleave ´BIAS´ value, the potential signal shifts accordingly. However, in my case, it only rotates(tilts) the ´Potential´ Scope, instead of shifting it, i.e. the magnitude of ´Potential´ Scope doesn´t change at all, just the slop changes.

  • | Post Points: 12

All Replies

Top 25 Contributor
55 Posts
Points 831
Bruker Employee
Suggested by Ang Li

I suppose you have tried on the sample chuck (D3100 stage) to see whether the measured potential follows the change in Bias. This is a quick way to verisfy whether the system is set up properly. Once you have done this, you can move on to your sample. For surface potential measurement, a reliable electrical connection to the sample is required; simply sitting the Si wafer on the chuck is usually not enough. It is recommended to scratch the back side of the wafer with a scriber then immediately apply some silver paste (paint) and glue it to a conductive sample puck. It takes 10 minutes for the silver paste to dry. Try this out and let me know whether this solves your problem.

Thanks

Chunzeng Li
Application Scientist, Bruker

Top 25 Contributor
58 Posts
Points 652

Hi Chunzeng, thanks a lot for your advise. I will try them out.

A new question, the silver paint has to be removed every time after measurements. Will it make the sample chuck dirty?

Although the si wafer is directly put on the sample chuck, the contrast seems not so bad. The ´dark´ particles are the inter-metallic compounds,on the top of Si wafer.

  • | Post Points: 12
Top 25 Contributor
58 Posts
Points 652
stsolong replied on Thu, Jun 21 2012 10:06 AM

surface potential.jpg.aspx

  • | Post Points: 10
Top 10 Contributor
129 Posts
Points 1,429
Ang Li replied on Mon, Jun 25 2012 12:53 AM

Hi, I guess Chunzeng suggested you glue the wafer on a sample puck that is usually for miultimode sample support, not to directly glue to sample chuck. 

Ang Li 

  • | Post Points: 12
Top 25 Contributor
58 Posts
Points 652

Hi Ang Li, you are right. I misunderstood Chunzeng´s suggestion. I will try then and report later.

  • | Post Points: 10
Top 25 Contributor
58 Posts
Points 652

Hi Chunzeng,

Thank you very much for your suggestion. I have a try and report here.

1) I used  a multimeter to verify the voltage on the sample chuck. When the Bias was 1V, the multimeter read as 0.25v. If I entered Bias 2v, the multimeter gave the value 0.5v. I guess some parts of AFM go wrong.

But anyway, the 'actual' voltage seems to be 1/4 of the Bias value. So I moved on to the following tests.

2)Then I have a try directly on the sample chuck. Unfortunately, the Potential scope was tilted as usual while changing in Bias.

3)As you suggested, I scratched the back side of the wafer with a diamond pen, and then immediately applied some silver paste (paint) and glued it to a conductive sample puck(a metal). It seems that it needs less Bias at which a good image can be achieved. For example, I used to apply 8 to 10 Volts Bias, but right now 5-7 volts.

Would you please explain me a little about the situation?

Thanks a lot!

Solong

  • | Post Points: 10
Top 25 Contributor
58 Posts
Points 652

Sorry, there is no bias voltage problem of AFM. I took the wrong component as reference(i thought it was grounded, but actually not).

The tilt of Potential scope is simply corrected by setting ´Realtime planefit´ to ´Offset´.  But it doesn´t  solve the root problem, does it?

Thanks a lot!

  • | Post Points: 12
Top 25 Contributor
55 Posts
Points 831
Bruker Employee

Realtime Planefit- Offset would not remove the tilt. Can you take a screenshot and send to me.

chunzeng.li@bruker-nano.com

Thanks

Chunzeng

  • | Post Points: 10
Top 25 Contributor
58 Posts
Points 652

Oh no, I know what a stupid mistake I have made.

The Potential scope was tilted because I didn´t notice that the ´Realtime planefit´was set to ´Line´ and ´Offline planefit´ to ´Full´.

Actually, the original Potential scope was not tilted. But ´Line´ planefit applies first order planefit on the Potential scope, which makes the Potential scope  tilt.

When I set ´Realtime planefit´  to ´offset´, the Potential scope doesn´t tilt and shifts to the center. But it is better to use ´Data center´ instead of setting ´Realtime planefit´ to ´offset´.

Both ´Realtime planefit´ and ´Offline planefit´ should be ´none´.

 

Please excuse me for bothering every body in  this topic.

 

  • | Post Points: 12
Top 25 Contributor
55 Posts
Points 831
Bruker Employee

No problem. It is not entirely your fault, we could have set the default to none.

Best

Chunzeng

  • | Post Points: 10
Page 1 of 1 (11 items) | RSS
Copyright (c) 2011 Bruker Instruments