Treatment of sample for analysis

Day 8

Sample cleaning

The day started off with the cleaning of the sample prepared yesterday.

This process uses acetone to "wash" away the organic portions of the die left, and by putting the die into a beaker filled with acetone, and putting the beaker into an ultrasonic cleaner, so that the dirts could be "shaked" away from the die.

After washing with acetone, the die is rinsed with alcohol, then blown dry, so that it can be clean for sample analysis. This process was fustrating, as the sample is rather small and light, and the blow gun have blown away my sample multiple times - once it even took some time for us to find it. Once the sample is blown away, it has to be washed again (which I did multiple times). Until finally, I successfully got the sample dry without dirtying it (much)



Under the microscope (before polishing)



Fig 7.1 Higher magnification (before polish)



Sample polishing

After cleaning the sample, it is time to polish it. Polishing the sample is meant to scrap away the top few layers so that the layers below could be seen for analysis.

First, a very rough polish is done. The sample is dragged across a sandpaper (grit 800) lightly 5 times.

The damage done:



After rough polishing



After rough polishing









 Only 5 times across the , see how badly it is damaged!

Next, a smoother pad is used, so that it can be more finely polished, such that the surface can be smoothed out again. particles of size 50microns were used for this part.

It was a long and extremely boring process.. I spent more than half an hour, doing exactly the same motion, trying to keep the path of motion consistant. Non-stop for more than half an hour. After putting it under the microscope, it is not much better than after the rough polishing. I do not have time to complete the polishing, as it was time to move on the the FIB (again)

after smooth polishing

after smooth polishing

FIB

Refer to day 4, Milling for previous experience with the FIB.
Today, Dr Ong showed me another usage of the FIB. After some brief introducion to the FIB, he showed me a different usage of the FIB - To cut the sample so that the cross section could be examined.

A layer of Platinum is deposited first to protect the area of interest



Cutting of the sample with an ion beam is done to create a hole



The cutting have to be done again to smooth out the edge

 

After smoothing of sample, and measurements made

 Notice the different layers of the sample? They are the metal paths, (top 2) and the transistor layer (bottom layer). All this are contained in 1 small die! (as shown in previous day's photo) Even then, we have only seem the top 3 layers, there are more below. This small chip contains all the information in our phones, computers, and many other electronic products!

That concludes day 8, do leave any comments on the chat box beside!