Maker Pro
Maker Pro

Semiconductor fabrication question

What happens if I sputter metal on top of an epiwafer, and then
sputter silicon on top of that metal? Iow, would the sputtered
silicon that is on top of the metal be amorphous or polysilicon or
what?


Thanks,
Anon
 
L

linnix

Jan 1, 1970
0
What happens if I sputter metal on top of an epiwafer, and then
sputter silicon on top of that metal?  Iow, would the sputtered
silicon that is on top of the metal be amorphous or polysilicon or
what?

Thanks,
Anon

Yes, you can deposit Metal or Polysilicon on wafers. Check with your
fab house for details.
 
Yes, you can deposit Metal or Polysilicon on wafers.  Check with your
fab house for details.


The reason for asking is Phil Hobbs said that sputtered silicon on a
PCB would result in a layer of amorphous silicon. I want the deposited
layer to be doped polysilicon, not doped amorphous silicon. So what if
I replace the PCB with an undoped polysilicon wafer? Actually I drew
an example of what I want to do. In the following image, lets say the
deposited method was to heat a piece of metal inside a vacuum, which
would slowly cause some of the heated atoms to fly on the wafer, and
next I would use the same method except it would be heated dopded
silicon instead of heated metal. This would result in a layer of metal
on the wafer followed by a layer of silicon (hopefully polysilicon).

http://sites.google.com/site/curiousjohn4/

Thanks,
Anon
 
L

linnix

Jan 1, 1970
0
The reason for asking is Phil Hobbs said that sputtered silicon on a
PCB would result in a layer of amorphous silicon. I want the deposited
layer to be doped polysilicon, not doped amorphous silicon. So what if
I replace the PCB with an undoped polysilicon wafer? Actually I drew
an example of what I want to do. In the following image, lets say the
deposited method was to heat a piece of metal inside a vacuum, which
would slowly cause some of the heated atoms to fly on the wafer, and
next I would use the same method except it would be heated dopded
silicon instead of heated metal. This would result in a layer of metal
on the wafer followed by a layer of silicon (hopefully polysilicon).

Vapor deposit of Polysilicon is standard procedure in any fab house.
They have masks for precision deposits of any Polysilicon or Metal on
wafers. I don't think they do it on PCB much, although it's possible.
 
Making poly requires high temperatures (usually about 550 C, iirc).  You
can do that by high-temperature CVD or by an annealing step after
depositing amorphous Si.

Cheers,

Phil Hobbs- Hide quoted text -

- Show quoted text -


Thanks for the info Phil! Slowly, but surely, I'll get it right. I
was told CVD is too dangerous for a garage operation. Wouldn't even
know where to buy the silane, and would be afraid to handle it. One
leak and kaboom!

The annealing step after depositing amorphous Si sounds hopeful for a
garage project. I'll start reading up on that semiconductor annealing
process, but haven't read about it yet. Sounds like some hope.

May I ask is GaAs easier to get in the crystal form?

Thanks,
Anon
 
Making poly requires high temperatures (usually about 550 C, iirc).  You
can do that by high-temperature CVD or by an annealing step after
depositing amorphous Si.

Cheers,

Phil Hobbs- Hide quoted text -

- Show quoted text -


I found the wikipage

http://en.wikipedia.org/wiki/Furnace_anneal

Lets say the junction plate width is are around 1um diameter, the
depletion width is very thin at 10nm for heavy doped Schottky, and
they are baked in the furnace at 550C to convert the amorphous silicon
to polysilicon. Any drawbacks to that process, perhaps enough metal-
semiconductor atoms diffusing to result in poor performance?


Thanks for any help and advice,
Anon
 
L

linnix

Jan 1, 1970
0
I found the wikipage

http://en.wikipedia.org/wiki/Furnace_anneal

Lets say the junction plate width is are around 1um diameter, the
depletion width is very thin at 10nm for heavy doped Schottky, and
they are baked in the furnace at 550C to convert the amorphous silicon
to polysilicon.

So, you agree that plastic (PCB) substrate is out of the question,
right?
Any drawbacks to that process, perhaps enough metal-
semiconductor atoms diffusing to result in poor performance?

You will not be able to preserve much of the semiconductor features
after annealing, unless you only want a block of polysilicon/metal
alloy.
Thanks for any help and advice,

Perhaps I misunderstood what you are trying to do and how you are
doing it.
 
So, you agree that plastic (PCB) substrate is out of the question,
right?


You will not be able to preserve much of the semiconductor features
after annealing, unless you only want a block of polysilicon/metal
alloy.




Perhaps I misunderstood what you are trying to do and how you are
doing it.




- Show quoted text -- Hide quoted text -

- Show quoted text -


Thanks. I'm a bit confused why Phil H. would say that I could anneal
the chip to convert from amorphous-silicon to poly-silicon if it would
destroy the chips properties.

It was said that CVD is too dangerous for a garage project. Are there
any other options we have not explored? What about solid-phase
crystallization (SPC), or perhaps metal-induced crystallization?

Thanks,
Anon
 
L

linnix

Jan 1, 1970
0
Here's a picture of my first goal

http://sites.google.com/site/curiousjohn4/

Note, in the final product, the green (deposited doped silicon) should
be poly-silicon, not amorphous silicon.

Thanks,
Anon

No semiconductor structure can withstand 500 degree annealing
temperature. In real life, polysilicon is annealed first, then
implanted into structures. You need the proper equipment and site to
do it. They (the fab houses) usually spend several hundred millions
dollars for them.
 
[snip]
Perhaps I misunderstood what you are trying to do and how you are
doing it.
Here's a picture of my first goal

Note, in the final product, the green (deposited doped silicon) should
be poly-silicon, not amorphous silicon.
Thanks,
Anon

No semiconductor structure can withstand 500 degree annealing
temperature. In real life, polysilicon is annealed first, then
implanted into structures. You need the proper equipment and site to
do it. They (the fab houses) usually spend several hundred millions
dollars for them.


I've made a lot of instruments that cost me practically nothing that
would have cost a furtune to buy. In this case I don't need fancy
equipment that's good for mass producing chips. So if it takes a week
per chip, then whatever.

I'm reading that if the amorphous silicon is on metal then it requires
far less temperature to convert it from amorphous to poly. Yesterday I
read that 150C is enough. I know most semiconductor components can
stand at least 220C. I don't know how thick the metal needs to be
though.

Another option, perhaps there's another method to deposit poly-silicon
other than CVD that is safe.


Anon
 
In real life, polysilicon is annealed first, then
implanted into structures.


As I told Phil Hobbs, the chunk of silicon that is to be heated up for
evaporation method is poly-silicon. I don't think that makes much
difference.


Why would CVD deposit poly-silicon on the surface, while evaporation
methods would deposit amorphous silicon? Perhaps if the evaporation
method was kept at an extremely low rate. Perhaps by lowering the
evaporation temperature. Of course lowering the evaporation
temperature would increase the time required to deposit the silicon.

Thanks for any help,
Anon
 
No semiconductor structure can withstand 500 degree annealing
temperature.


I'm sorry, I may have misunderstood your sentence. I would agree that
a semiconductor component would not survive that temperature very long
because the plastic casing would melt. I just read at wikipedia that
CVD uses temperature around 650C to deposite poly-silicon. So I'm
guessing that the raw chip without the plastic casings can handle
those temperatures.

Phil Hobbs, are you around. Could you please clarify?


Thanks,
Anon
 
I'm sorry, I may have misunderstood your sentence. I would agree that
a semiconductor component would not survive that temperature very long
because the plastic casing would melt. I just read at wikipedia that
CVD uses temperature around 650C to deposite poly-silicon. So I'm
guessing that the raw chip without the plastic casings can handle
those temperatures.

Phil Hobbs, are you around. Could you please clarify?

Thanks,
Anon


To clarify, when I say "evaporation" I am referring to either method,
evaporation or sputtering, whatever method works best. My fault.


Anon
 
L

linnix

Jan 1, 1970
0
I'm sorry, I may have misunderstood your sentence. I would agree that
a semiconductor component would not survive that temperature very long
because the plastic casing would melt. I just read at wikipedia that
CVD uses temperature around 650C to deposite poly-silicon. So I'm
guessing that the raw chip without the plastic casings can handle
those temperatures.

Here is something describing the silicon junction breakdown at around
200C to 300C. I did not read the detail, but I think it is in the
right ball park figure.

http://adsabs.harvard.edu/abs/1969JaJAP...8..917O
 
Here is something describing the silicon junction breakdown at around
200C to 300C.  I did not read the detail, but I think it is in the
right ball park figure.


You know, it may be possible that a low temp below 200C annealing
process done for a very long time could work over and over might
convert the amorphous to polysilicon. It may not be mentioned in the
industry because it would be impractical, too slow, but I have plenty
of time. In this case the silicon is on top of metal, so that also
helps.

Thanks,
Anon
 
L

linnix

Jan 1, 1970
0
You know, it may be possible that a low temp below 200C annealing
process done for a very long time could work over and over might
convert the amorphous to polysilicon. It may not be mentioned in the
industry because it would be impractical, too slow, but I have plenty
of time. In this case the silicon is on top of metal, so that also
helps.

My factory needs 10 to 15 weeks for CVD of a 15um device with 4
masks. How slow do you want to do yours, even if it makes any
difference.
 
My factory needs 10 to 15 weeks for CVD of a 15um device with 4
masks.  How slow do you want to do yours, even if it makes any
difference.- Hide quoted text -

- Show quoted text -


That doesn't sound right. Maybe they meant 10 to 15 hours. I'm reading
everywhere that CVD is around 15nm per minute. It would take just over
16 hours for 15um.

I wouldn't need nothing close to 15um anyways. More like 15nm, which
would take one minute. I'm willing to wait one week.

Thanks
Anon
 
L

linnix

Jan 1, 1970
0
linnix said:
[snip]
Perhaps I misunderstood what you are trying to do and how you are
doing it.
Here's a picture of my first goal
http://sites.google.com/site/curiousjohn4/
Note, in the final product, the green (deposited doped silicon) should
be poly-silicon, not amorphous silicon.
Thanks,
Anon
No semiconductor structure can withstand 500 degree annealing
temperature. In real life, polysilicon is annealed first, then
implanted into structures. You need the proper equipment and site to
do it. They (the fab houses) usually spend several hundred millions
dollars for them.

Nonsense. Rapid thermal anneals of 900-1100C are common.

And you don't think it will anneal everything explosed?
 
L

linnix

Jan 1, 1970
0
linnix said:
linnix wrote:
On Nov 17, 10:56 am, [email protected] wrote:
[snip]
Perhaps I misunderstood what you are trying to do and how you are
doing it.
Here's a picture of my first goal
http://sites.google.com/site/curiousjohn4/
Note, in the final product, the green (deposited doped silicon) should
be poly-silicon, not amorphous silicon.
Thanks,
Anon
No semiconductor structure can withstand 500 degree annealing
temperature. In real life, polysilicon is annealed first, then
implanted into structures. You need the proper equipment and site to
do it. They (the fab houses) usually spend several hundred millions
dollars for them.
Nonsense. Rapid thermal anneals of 900-1100C are common.
And you don't think it will anneal everything explosed?

Sure, but so what? Annealing is what the OP wants. I wouldn't bet any
important money on his succeeding, but it sounds like a fun project, and
we should at least make sure he gets good info.

But he did not want to anneal everything, including the substrate. It
will not be the same structure afterward. Of course, he can mask and
etch them out, but not simple annealing.
 
Top