Can Teflon Tape Withstand the Attack of Etching Solutions?

  • Thread starter depot123
  • Start date
  • Tags
    Etching Si
In summary, the conversation is discussing the best method for etching 525um of p-type silicon. The individual is considering using HF+HNO3+CH3COOH for a high etching rate, but is also looking for a mask that can withstand the corrosive mixture. Anisotropic etching is suggested as an alternative, using a KOH/IPA mixture, which is safer and easier to work with. The individual also asks about using teflon as a mask, but there are concerns about how it will be deposited and etched. The conversation also touches on the size and shape of the pattern being etched and the potential effects on a copper pillar beneath the silicon.
  • #1
depot123
5
0
Im trying to etch 525um (100) p-type silicon, and i intend to use HF+HNO3+CH3COOH for high etching rate since i need to etch 525um of Si. does anyone know what ratio should i use to obtain high etching rate?

I am trying to look for a mask that is able to withstand the attack of the etching solution, would the teflon tape withstand the cp4 attack? if not, can anyone with experieces let me know what can withstand etching solution's attack?

thank
 
Engineering news on Phys.org
  • #2
Below are a couple of references to get you started. The problem with HF/HNO3/CH3COOH is finding a mask that will with stand this very corrosive mixture long enough to etch through the silicon. I suggest you look instead at anisotropic etchants instead. A simple KOH/IPA mixture will etch through the silicon and is easily masked with SiO2. Plus it is much safer and easier to work with.https://www.seas.upenn.edu/~nanosop/documents/IsotropicSiliconEtch.pdf

https://www.ee.washington.edu/research/microtech/cam/PROCESSES/PDF%20FILES/WetEtching.pdf

https://en.wikipedia.org/wiki/Etchi...t_etching_.28Orientation_dependent_etching.29
 
  • #3
Thanks for reply, if I use anisotropic KOH, it will etch very slowly once it hits 111 plane, then I won't be able to etch through the 525 um thickness, so I should use corrosive HF/HNO3/Acetic acid method.

I'm wondering if it is possible to use Teflon as a mask to withstand its attack? Such as the Teflon etching cell like this http://sailorgroup.ucsd.edu/research/porous_Si_intro.html
 
  • #4
depot123 said:
Thanks for reply, if I use anisotropic KOH, it will etch very slowly once it hits 111 plane, then I won't be able to etch through the 525 um thickness, so I should use corrosive HF/HNO3/Acetic acid method.

What does the pattern that you are trying to etch look like? How small of a pattern are you trying to etch all the way through the silicon? Bear in mind that with an isotropic etch it will etch sideways at least as far as down. So the minimum pattern that you can etch will be 2* 525 microns. You could achieve the same result by upsizing the pattern by 525 microns per side and using an anisotropic etch. As long as the pattern is larger than 2 * 525 microns, the anisotropic etch will etch all the way through.

I'm wondering if it is possible to use Teflon as a mask to withstand its attack? Such as the Teflon etching cell like this http://sailorgroup.ucsd.edu/research/porous_Si_intro.html

I don't know. Maybe. How will you deposit and etch the teflon?
 
  • #5
my die is about 9x9 mm and i am trying to etch a square of 7x7mm on the center of the die, so it is quite large.
I have a question about anistropic etching using such as KOH, the etching rate would dramatically slow once it hit the 111 plane of silicon, resulitng a praymaid like etched structure, which is not what i want. Therefore, i am thinking it would be better to use isotropic etching, which it won't have such problem.
 
  • #6
With anisotropic etching you will get an inverted pyramid with well defined sloped sides. With isotropic etching you will get rounded sides and the degree of rounding will depend on exactly how long you etch - it will be very hard to control. Do you want the opening 7mm wide at the top or at the bottom?

But it is your choice. If you use isotropic etching with teflon as a mask, how will you deposit and etch the teflon?
 
  • #7
i would like to have the opening 7x7mm at the bottom. I have bonded copper pillar beanath the silicon die; i need to etch 7x7mm Si on the top to all the way down to the bottom in order to see the bonded structure.

If i use teflon as a mask, I am planning just ot use teflon tape, which is can tape around the die tightly and tape it in place on the teflon glass container, and then pour in the etching solution to it, and it will etch the exposed region on the silicon die. That is how i am planning to do, but i haven't had any Si etching experience before.
 
  • #8
(1) I predict that the HF/Nitric/Acetic will eat away the adhesive on the teflon tape and you will end up etching away all of your silicon.

(2) What do you expect to happen to your copper pillar when the HF/Nitric/Acetic reaches it?
 
  • #9
1) really?, then i might look for anther way in which customize a teflon cell/holder so i can mount my silicon die onto the teflon holder with exposed 7x7mm square on the top where i can pour in etching solution, just like the etching cell sailor's lab is using http://sailorgroup.ucsd.edu/research/Standard_cell_top_tapped_all.pdf
do you think it will work?

2) actually, i have Ni coating on the outside of copper pillar, and as long as i could keep track of as it apporach to the end of 525 um Si, it won't etch that much of my structure.
 
  • #10
Well, I'm pessimistic, but maybe I'm wrong. Go ahead and try your scheme and see if it works.
 

1. How do I prepare the (100) p-type Si substrate for etching?

The first step in preparing the (100) p-type Si substrate for etching is to clean it thoroughly. This can be done using a solvent such as acetone or isopropyl alcohol to remove any particles or contaminants on the surface. Next, the substrate should be rinsed with deionized water and dried using nitrogen gas.

2. What type of etchant should I use for (100) p-type Si?

The most commonly used etchant for (100) p-type Si is hydrofluoric acid (HF). This acid can etch the silicon substrate at a controlled rate, producing smooth and well-defined features. Other etchants such as potassium hydroxide (KOH) or tetramethylammonium hydroxide (TMAH) can also be used, but they may produce less uniform results.

3. What is the etch rate for (100) p-type Si?

The etch rate for (100) p-type Si can vary depending on the type and concentration of the etchant used, as well as the temperature and agitation of the etching process. Generally, the etch rate can range from 10-100 nm/min for HF etching, and up to 10 um/min for KOH or TMAH etching.

4. How do I control the etch depth of (100) p-type Si?

The etch depth of (100) p-type Si can be controlled by adjusting the etching parameters such as etchant concentration, temperature, and agitation. It is also important to monitor the etch rate during the process and stop the etching at the desired depth. Using a mask or patterned resist can also help to control the etch depth by protecting certain areas of the substrate from etching.

5. What safety precautions should I take when etching (100) p-type Si?

When working with etchants, it is important to follow proper safety precautions. This includes wearing protective gear such as gloves, goggles, and a lab coat. HF etchant is particularly hazardous and should be handled with extra caution. It is also important to work in a well-ventilated area and dispose of the etchant properly after use.

Similar threads

  • Biology and Chemistry Homework Help
Replies
4
Views
2K
Replies
16
Views
2K
  • Science Fiction and Fantasy Media
Replies
7
Views
3K
Replies
63
Views
13K
Replies
10
Views
12K
  • Materials and Chemical Engineering
Replies
2
Views
6K
  • General Discussion
Replies
4
Views
7K
  • MATLAB, Maple, Mathematica, LaTeX
Replies
7
Views
2K
  • MATLAB, Maple, Mathematica, LaTeX
Replies
7
Views
3K
Back
Top