You can’t cheat physics…

…and neither can I.

So, where have I been? Up to no good, apparently.

Up until now, I have skipped altogether the way I was going to pattern the chips. The thing is, you can either have not super expensive paterning tools and expensive resists, or expensive tools and cheap resists.
Obtaining the expensive resists is, well…expensive, plus they are very especialized and sensitive. Also, the optical setup needed is not an easy task either. While looking into it, I found out that acrylic (PMMA) can be used as resist, however, it requires e-beam paterning, wich in turn means you need an electron microscope, wich is not cheap.

Some countries have kind of a market for secondhand electron microscopes, however mine doesn’t. The thing is, if you don’t actually need to scan the thing, but just to shoot electrons at it, could you use any other electron gun?

In theory, you could. It is not a question of voltage (this paper talks about very low voltage PMMA paterning) but to get the assembly to the adequate vacuum conditions. It is not enough to have a good mechanical vacuum pump.

In case you don’t believe me, here’s what a CRT tube does in 40 microns of Argon vacuum:

Here’s the setup:

Having proven that I needed a High vacuum pump, I started working on an oil diffusion pump.

However, the pieces I practiced on where 0,5mm stainless, wich proven trycky, but doable. The final pieces where only 0,25mm thick, wich, unfortunately, altough possible in short runs, it did pierce the sheet on start, wich left the pieces unusable. Shame, they where looking gorgeous:

Now that I had to start again and spend more money on it, a consensus was reached between me and an expert (to be mentioned when, if he, permits it) to try to go for a turbomolecular pump, wich are quicker to reach and stop vacuum, clean in their operation and they look like miniature turbines, wich, to be frank, turns me on. XD

 

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The Goblet of Fire

Plasma, that fourth state of matter:

-“When an ionised gaseous substance becomes highly electrically conductive to the point that long-range electric and magnetic fields dominate its behaviour.”
(wikipedia)

As you know, plasma is a quite hot stuff. Usually it’s density is so low that thermal transfer quickly reaches an equilibrium much lower than the melting point of materials. However, in a sputtering machine, you do concentrate plasma in a small area, so, continuous operation requires a bit more than just having a passive aluminium heatsink.

And yes, you can just powermelt the target:

An aluminium plate with concentrated plasma heats quickly, as I have found out. After medium sputtering runs (20/25 minutes, NO Argon), the magnets are so hot you can barely hold them in your hand. That must be around 40/50ºC, wich obviously can only get worse. Normal (cheap) neodimium magnets have a curie point of just 100ºC, so it’s better not to risk damaging them. And just because fuck yeah, I want to liquid cool it to allow extended operating time.

Let’s have some water channels cut into the plasma trap plate:

At first I was thinking about machining it by hand in stainless, as having a rotary table makes it a fairly easy task. However, later on, I realized I could simply make it in aluminium wich is a better heat conductor AND my 3020CNC can machine it, if you are patient. I’ll still have to tap all the holes by hand, but that’s a minor nuisance.

Having a laser cutter helps immensely with reducing waste (milling acrylic is a pain in the ass)

Some might say so many screws are overkill, and might be true, however, given the diameters involved, and that I am using viton O-rings wich are not super flexible either, I have just preferred going all the way. The acrylic is 7mm to ensure minimum deflection.

Yeah, I should have made the utside border a tad larger. (The inside diameter has to fit the magnets, so there’s not much room there.)

The screws are stainless steel, so I don’t think they will affect the shape of the magnetic trap.


Test fit on top of a non machined plate (with recess for the magnet)

Since I received my new 3D printer before machining the plate, I printed a 15mm section to test fit the magnets and general visual guidance, plus screw check.

The magnet slot had a bit too much room left (2mm) so it was reduced 1,25mm in Fusion. (to 40,75mm). The screw lenght allowance was correct.

Overall fit was good, so the minor changes where validated and saved.

Machining!

Spot drilling.
I was too lazy to actually make a separate program for this, so I used the same drilling program, but added a +6.5mm offset so it would only peck 1.5mm with the 90º spot drill, I know, extremely ineficient, but it would have taken longer to start the computer and actually make the program.

After drilling, the o-ring recesses where cut.

Quick seal check, just in case y messed up, or the o-rings where wrong.

As an afterthought, I could ave made the slots 0,5mm deeper, so the acrylic would fully compress the rings and sit flat against the plate, but well, as I said, an afterthought.

The magnet slot was cut first:

Then the water channels:


I know the pic is shaky, but I was busy, you know…

Little misshap with mach 3 going first to Z-Ø instad of X/Y-Ø, and a not-so-exact Z height setup. Fortunatey, the cut was ony 0,15 deep, so it doesn’t affect the overall performance, just my inner pride. (I tested a newish 2-flute endmill instead of the oldish 4-flute I was using, but it underperformed, so I changed back, and messed with the paper thickness Z height procedure. This part is not critical in the Z axis, so I wasn’t particularly worried.

Anyhow, everyone hail the awesome cooling plate:

I accept the fact that there will be some blow-by between inlet and outlet, but most of the water should still flow along the path.

Magnets!

The CNC part took 6.5h to machine in a cheap (ballscrew) 3020CNC router, with the following setup:

  • 2mm carbide 90º spot drill, 2,5mm carbide drill.
  • 8mm depth, 0,25 pecking depth. Lube between holes.
  • 2mm (R1) carbide ball endmill.
  • 4mm-4flute carbide endmill, flat, center cutting.
  • 0.5mm depth of cut up to 5mm depth (6mm for magnet), 1.25mm stepover. 75mm/min plunge. 150mm/min feed.
  • LUBE as if there was no tomorrow. Also make sure all the router bolts are tight.

These kind of machines are not particularly rigid, so this is the absolute limit of what they can do. If you are patient, tough, you will be able to squeeze it to the very last drop.

Using a locating setup, one could just machine the outside border and flip the part to machine the lip, however, since I have a lathe, I just prefer to do it there and avoid the hassle.

First, bandsaw the corners.

Chuck the plate from the inside…

…and slowly carve the diameters away.

After polishing all the important surfaces:

Oh! Also some custom fittings should be made, amirite?

So gorgeous.

In the heat exchanging department I would like to employ some passive cooling like this:

I know I could try to hook it up to one of my beer refrigeration units, however I pretty much prefer not to, because the vacuum chamber is at potential, and having liquid wiring around is…well, not my thing. Also it will make for a standalone unit (not that it is going to go anywhere, but hey, what if I want to sputter in the living room?) Should that not suffice, I can always connect it to one of the machines later, or make a heat exchanger or something.

In any case, the particulars of the radiator are irrelevant, any liquid computer cooling setup should work (to some extent, if you put a small one). So, pick your poison, as some say.

See ya!

Doc Ock, (part 1)

Ladies and gentlemen, fasten your seatbelts.

Doc Ock. (Spider-Man, 2004)

 

As we have seen before, my vacuum chamber is compact. That has benefits and drawbacks.

Pros:

  • Quick vacuum: Less volume means less time to achieve working pressure.
  • Easy to mantain and clean.
  • No need for expensive feedthroughs for power (because glass wall isolates A-K)

Cons:

  • Limited space.
  • One experiment at a time, posible contamination between changes of target.

Of course, the volume is the one it is, that can’t be changed, however I can do some things to manipulate the contents of the chamber and outperform bigger chambers.

 

Glass & Magnets: Trollscience.

Making feedthroughs for vacuum is no easy task, materials must be taken into consideration, as well as the air-tightness of the interface. Since I’m already into glassworks, I have an extended range of materials to choose from, making it a bit easier.

With 10mm separation, it’s possible to make full turns without stage interference (magnet-magnet through glass force being much greater than the interaction between heights.

It should look like this once finished:


Materials:

  • Internal magnet supports: Teflon
  • Axles: Stainless steel with HVAC grease to inhibit galling.
  • External actuation, probably 3D printed in PLA.

The external means of actuation must provide independent rotation for each axle AND whole assembly vertical displacement. It will either be purely mechanical or probably, servo driven for more flexibility in controls placement. But it is trivial in comparison to the rest.

 

The other end of the magnetic stick.

Or when small, can be too small (but still work).

 

It is obvious that laparoscopy is the main inspiration here, with some really cool, purely mechanical setups. Keep in mind, tough, that the angular requirements and constraints we face are somewhat different, plus we don’t need some of the capabilities of those efectors.
After a succesful simple joint test, I jumped into the whole arm design:

It’s a SCARA arm with a nonrotating wrist (just side to side).

Assembly process:

Nested axles and actuactor cables:

Glory to the all-reaching hand!

@0:13 – Bitchslap!

Bad printing in the hand section prevented me from testing the gripper, but seriously, if you are not impressed by now, go fuck off.
With this I should be able to perform elaborate tasks WHILE under vacuum. I can have racks inside the chamber for target and substrate change and can try simple masking too.

  • Axle diameter, 1,5mm
  • Biggest arm diameter, 4mm
  • Total lengt, 50mm
  • Actuator wires 0,2mm

It will be built slightly bigger in stainless, with teflon axles and braided stainless steel cables. And yes, the most important thing, I will put TWO of these inside, because who doesn’t want to stick their hand in the sun?

Seriously, it’s going to be fucking EPIC.

 

Thunderdrome. (lightning in a bottle)

Let’s make a sputtering chamber HV power supply on the cheap!

From left to right:

  • AC source. (220V wall socket)
  • Variac 3000VA. (probably a smaller one works)
  • Microwave transformer, stock.
  • HV rectifier.
  • Microwave capacitor with built-in parallel resistor for self discharge safety.
  • Vacuum chamber.
  • Homemade needle valve for gas, mainly Argon.
  • Main vacuum valve.
  • Two stage rotary pump.
  • MISSING: 100Ω current limiting power resistor. I haven’t received/installed it yet.

All components get mounted with nylon screws on top of a PVC plate AND a steel support connected to ground.

Mockup of component placement.

All sputtering I have seen around, reports in their setups about 500V tops, and around 500mA max. Most 2KV diodes I saw in ebay where low power, and I didn’t felt like risking a failure there, so instead I looked for power diodes, no matter what the voltage. I ended with 20.000KV 2A diodes, you can call that overkill, if you want. XD!

Silicone cable was employed everywhere. Long sections were further insulated with transparent PVC tubing:

Transformer and diodes ready:

The capacitor was zip tied to two adhesive nylon stands:

PVC sleeved cables go through the case using M12 plastic glands and go up to the chamber plates.

I also got hold of a nice fancy WERMA beacon for safety? (bling, XD)

However, as hard as I tried, the USB-rgb capabilities were imposible to activate, my computer could not even detect the fucken thing. In the end, I decided I don’t need all 256 bits of RGB color, and just hardwired the leds themselves.
I would have much preferred to remove the chip and such, but the whole thing is IP68 sealed, trying to open it would only destroy some of the plastic. It doesn’t seem to mind me hardwiring the leds, so there it is.

Now, let’s get some color!



Will build a 10,05Mohm HV voltage divider with a 200 to 1 ratio, and connect it to two comparators, one inverting for green, one normal for red.

I plan to have dedicated voltage and current meters (I want my multimeters avaliable elsewhere), so I’ll use cheap ones from ebay, having them battery powered, to save on the hassle of tapping into the HV line. Or tap into mains line, and risk having spurious currents/voltages deriving from the HV section into the mains section.

See ya!

The Chamber of Secrets. (How it’s made edition)

(I lost some of the aluminium machining pics, so I used the stainless steel ones, wich look practically the same).

Rough cut:

Interrupted cut:


Changing from aluminium to stainless is a pain in the ass, believe me.

For the aluminium, I machined a groove in the mill:

At first I thought that keeping the seals captive was the best option:

However, as good as the milling looks, it wasn’t as mirror finish as I would like, leading to leakage problems.

After thinking a lot about how to polish it, I came to the conclusion that the outside lip was just giving me problems, so I ended removing it, wich also made polishing the resulting flange surface a breeze.

Back to stainless:

Once the disc was at size (125mm, just 2mm wider than the seals), the side flange was cut:

At this point, the disc is finished, but a rough surface is really not desirable for the inside of a vacuum chamber.

Since the disc was held with double sided tape only (tailstock for outside machining) I really, really, carefully trimmed the surface (0,02mm passes), then polished it too.

Once that was done, some viton rubber seals where cut. Viton is not super flexible, so your chamber walling needs to be fairly flat in the edges (Mine isn’t and requires some persuasion to start pumping down, then it goes fine).

I also use two viton o-rings to keep the glass bell centered, just in case.


Looks frikin’ legit, IMO.

Forgot to adress something. Why change from aluminium to stainless?
KF16 (and all other KF joints, for that matter) come mostly in stainless steel, especially weldable connectors like this:

I bought one before finding a stainless supplier, but even then, for the cost (I think it was 8€) I much prefer to just buy and save machining time/inserts/material. Altough I have material from wich I could have machined an aluminium adaptor, welding aluminium is a pain in the ass, compared to stainless, iron and similar, so, even if having found a cheap place to buy stainless stock, I just went for that (buying the piece).

For the first tests with the aluminium plates, I used an M8 to 1/4SAE adaptor and connected one of the plates to the refrigeration vacuum pump, and on the top plate, turned a recess to put the magnets as close to the vacuum wall as possible:

The glass bell is a 100mm ID borosilicate, 5mm thick, beer machine viewport. I know many people just use canning jars or whatever glass encasings they can find.
And at first I considered it too, because I could not find any supplier of borosilicate tube in bigger enough size (that was affordable). One day as I was about to go to sleep, I just gave internet a last go, and lo and behold! I found one homebrew beer supplier that sold them at a decent price.
In the photo they have square edges, but mine came with them flame polished, wich is not bad either.

And where does all that sit?
In a BEKVÄM table, of course. It seems to be the go-to support for things like this, and other stuff.

And that is mostly it, next time, HV power supply (2Kv).

See ya!

Glassworks!

Because I am a cheap bastard that wants to use the endcaps of my vacuum chamber as Anode and Katode, Instead of messing around with spark plugs or similar, I need an electrical insulator for my vacuum pump, because the KF16 vacuum line is all metal. Otherwise the pump would sit at 500V potential!
Buying a ceramic insulator is out of the question, and a glass insulator is expensive (could easily reach 100€, SUPPOSING that the selling company wants to do business with an individual). So, I bought borosilicate tube and set my lathe to slow cooking.

Hmmm, looks like the part, doesn’t it?

It fits:

It closes:

Aaaaand…it breaks. (WAS expected, it doesn’t have the proper 15º slope, for starters)

This was done with absolutely ZERO effort, just heating the glass and poking it with a graphite rod.

Next: Proper glassworks with graphite mold.

Passing gas.

Since we previously established that ball valves aren’t the best both at keeping high vacuum AND letting small gas quantities into our devices, it was clear that one more suitable (and affordable) had to be made.

Temporary plans (changed it whilist machining):

Designing process done, it’s time to machine. Everything is stainless steel  304 (except the bearings, I know).

UP: heavy turning (for my lathe), that’s 2mm chips. DOWN: some more machining.

Unfortunately, I didn’t catch all the machining process, I got very busy with it. Here’s the final product (minus the o-rings):

Fitting is not critical, but making it a good one, is best practice:

That’s some small axial bearings! (3x6x3mm). The knob is smooth because since the plunger rides on bearings, nothing should ever be stiff enough to require knurling. (also, I don’t have a knurler :P ) As you can see from the timelapse, I changed the screw design into a prong extension, easier to machine and allows for simpler play adjustment.

The ball bearings allow the actuation of the plunger without o-ring twist, both up and down. (the up might be a bit overkill, but hey, I already got the bearings, you know).

And most importantly, the gas connection:

It accepts 2mm RC compressed air tubing.

Also, do you need one? They’re for sale!