E-beam lithography for nano size electrode

I will explain about e-beam lithography later.

Today, i just want to show the image of electrode.

The smallest size is 50 nm.

I used A11 for the base PMMA.

The A11 PMMA was mixed with A thinner to obtain A3~4.

The mixed PMMA shows also good resolution.

And the lift-off of pmma is very fast.

We also tried patterning using A1 PMMA. 

Lift-off process was really hard.

Our PMMA was rapidly lift-off.

The pattern was not clean.

I'm going to make more clean and shape pattern for 20 nm.

If you have a good idea, do not hesitate to contact me!

I want to share the good information about e-beam lithography.
Moreover, I want to share about graphene and boron nitride as well!

The figure shows electrodes size of 100, 50, 250, 100, 100, 200, 200, 200 nm.

See you~:)

Brief review for 2 dimensional materials(Graphene, MoS2, BN)

Nowadays, several two dimensional (2D) material was studied with its unique properties. The figure shows various 2D materials such as Graphene, Molybdenum disulfide (MoS₂), Boron nitride (BN), and hybrid structure of 2D materials (graphene on BN in this figure). The graphene has been experimentally discovered few years ago by Phillip Kim, A.K. Geim and their coworkers. They used mechanically exfoliation method for separating layers from graphite as shown in Figure (a). Graphene has various unique properties such as high mobility, possibility of quantum effect at room temperature, ambipolar electric field effect and application for flexible and transparent devices. Recently, the MoS₂ field-effect transistor shows fantastic performance with Hafnium Oxide used for dielectric layer, (It was published in Nature nanotechnology). It has not only higher mobility than silicon but also high On/Off ratio. The BN was suggested to replace silicon dioxide deposited substrate which is usually used for graphene substrate. The graphene devices show enhanced properties on BN due to elimination of charge trapping, rough surface, and the same hexagonal structure (It was also published in Nature nanotechnology). The figure (d) shows BN/graphene structure by using stacking process which had been posted yesterday on my blog.

Optical images for (a) Graphene, (b) MoS2, (c) BN, and (d) hybrid 2D structure.

Apple bluetooth keyboard

I always use "bluetooth keyboard" for my iphone 4s!

The keyboard in iphone display is too small!! i can't type for my message!!

If you use bluetooth keyboard, it will make you comfortable :)

These are my ipad and bluetooth keyboard

size

 beautiful Korean baby~

Bluetooth keyboard

Right side of bluetooth keyboard shows power button.

If you already make a connection between product (iphone or ipad) and keyboard, 

the connection will be automatically performed by pushing~ power button.

When you want to change battery for your keyboard, you should open left side of your keyboard~ and change it!

Do you want to buy this one?

Whatever you think something, i really comfortable with bluetooth keyboard.

However, i think it doesn't need for ipad.

Ipad has a little big keyboard on display compared to iphone.

I tried to make document with ipad and bluetooth keyboard...

I feel that "Now, it is the time to turn on my computer immediately."!!!!!!!!!!!!!!

But simple document is okay~~

Anyway, really Nice!

ENJOY YOUR IPAD AND IPHONE with bluetooth keyboard

IPHONE 4S and 4. select your case, carefully!!

I'm using ipad 2 and iphone 4s.

If you have ipad2........omg..

If you have iphone !

I recommand, "Do not buy ipad!"

Ipad was puchased longtimes ago.....

when i get a iphone4s, ipad is going to far away from me......

This is my iphone4s ! 

This is my iphone 4s !

It has a same design with iphone 4.

Up (4)/Down (4s, that's mine :)

The picture shows different position of hold key.

When you select your case, you should careful for design of case.

Some case will not be fitted to your iphone.

If your case has a big hole for side part which includes hold, volume keys, 

the case will be okay.

Remind it ! :)

Exfoliation method for graphene and boron nitride (BN)

Graphene

Boron nitride

The graphene and Boron nitride (BN) could be exfoliated by mechanical exfoliation method.

Recently, BN was successfully used to replace substrate for graphene.

As you know, the graphene device shows the excellent property on BN.

I think that the other material also could be used for it.

I hope somebody will find it and get a publication in Science and nature!! :)

Boron nitride (BN) and Graphene stacking process

Thesedays, the Boron nitride (BN) is very promissing material for high quality of graphene device.
They have a same hexagonal structure.
Graphene device shows fantastic performance with BN.

The graphene devices on SiO2 has problems such as charge trapping and roughness....etc..
Graphene is one atommic layer which could get a huge affection with various substrates.


Now, I'm doing the stacking process for graphene and BN.
My result is posted below this text.

Dr. Bang is going to make e-beam lithography pattern, I hope he will get  a successful result....
Let's go!! BN/Graphene!!




요즘 BN이 한창 뜨고 있다.
그이유는 그라핀과 같은 Hexagonal structure이기 때문이지.
Graphene이 SiO2웨이퍼 위에서 본래의 성능을 내지 않는 것은 모두가 잘 알고 있다.
이유인 즉, Charge trapping도 있고, roughness문제~ 등등이 있을 것이다.
Graphene이 워낙 얇은 (one atomic thick) 이다 보니, roughness란 아주 중요하다.

현재 BN과 Graphene을 적층을 하고 있다.

앞으로 이빔 패터닝을 곧 해낼 것인데, 연구실 내에 미스터 방연구원이 어서 해내어 주길 바란다.

으으.........너만 해내면 된다...방! 화이팅.....

그림은 본인이 만든 Graphene과 BN 적층 구조이다. 곧 이 위에! 소자를 만들리!
교수님과 함께 힘을 합쳐 ㅋㅋ!!


그럼...See you

Optic lithography for 2 um pattern

Photo Lithography


For 2 micrometer pattern using photo (optic) lithography

Material : wafer, AZ-5214E, MIF-300

1. You should clean your wafer with acetone, IPA, DI-water.
Usually, the wafer cleaned in ultrasonic bath for Acetone and IPA.

2. PLZ, Annealing your pre-cleaned wafer on Hot plate at 100 degree celcius for 10 min.
I postulate that the post heating process will give you the more better condition of surface.
Because the residue of moisture will be removed by post annealing.

3. Spin coating, AZ-5214E, There is a three step.
4500 (3s), 6500 (5s) 8000 (20s).

4. Soft bake process at 90 degree celcius for 1 min.

5. First exposure under your mask for 1~2 seconds.

6. Hard bake at 130 degree celcius for 75 seconds.

7. Second exposure with our mask (Blank exposure) for 60 seconds.

8. Develop with MIF-300 developer.

9. Done.

This is for negative pattern process.

If you can not get the good pattern~ give me a reply~~:)



많은 연구실에서 Photo (optic) lithography를 사용중이지.

우리도 그렇다, 우리도 정말 하루도 빠짐 없이 거의 사용한다.
현재 약, 2 um 선폭까지 가능하다. 물론 대부분의 연구실에서도 가능하겠지만,
혹시 모르고 있을 내 친구들을 위해 써보아요.

1. 웨이퍼를 깨끗하게 씻어라. acetone --> IPA --> DI-water 순으로 깨끗하게 씻어라.

2. 씻고 난다음, 가열 한번 해주라. 100도에서 약 10분? 남은 수분을 날려 버리고 싶다.

3. 본 연구실은 AZ-5214E를 사용한다. Negative, positive 모두 가능하다.

4. 본 문에서는 Negative에 대해서 쓰도록 할게요.

5. 아놔. 이제 존댓말 써야겠어요....

6. Photo resist (PR)을 웨이퍼에 Spin coating한다. 4500 3초, 6500 5초, 8000 20초 합니다.

7. Soft bake 하셔야죠? 약 1분 정도 합니다. 온도는 90도.

8. First exposure를 합니다. 시간은 1초~2초 사이.

9. 2 um를 기준으로 쓰는거에요. 작은 선폭일 경우, 저 정도의 시간이 딱 적당 했습니다.

10. Hard bake 하셔야죠. 1분 15초 합니다. 몇도? 130도에서.

11. Second exposure를 합니다. 60초 해줍니다.

12. DEVELOP (MIF-300) 해줍니다. 보통, 25~35초 정도 합니다. 그리고 물에 씻어 주어요.

그러면 2 um의 resolution을 얻을 수 있습니다.

안되면 댓글~!




감사감사!

Gap 및 선폭 모두 2 um 이다!
뭐..이제 연구실 내부 모든 사람들이 이 정도는 만든다.
1 um대로 마스크를 만들려고 하니, 가격이 갑자기 높아 지더라구요~
흠.....
그건 이빔으로 하자!