Discovery of a nation!

Through the time of our primary and secondary school education all of us have by ourselves built an idea of what our country represents. This might be the general notion the society in which you grew up has in their mind. A thing that happens when you start to travel outside your native land is, that you see how different things are; in different parts of the world. And in India, things are wayyy more different from one place to the other.

This has always made me ask myself, what are we, or rather what does this nation stand for, only to find myself perplexed. But it didn’t matter that much, even when once my Professor Dr Reuben Wong asked us, discussing the difference between China and India with Europe, is India a group of small nations, or is it one single big nation.  

But recently, after seeing some rather uncomfortable claims  made by some religious propagandists, and politicians who use their support to their advantage, I started to feel the necessity to define at least to myself, what is our nation, and what does it stand for…

It is high time I did this to myself, before I start believing the false histories and stories that float around on the internet, teaching people very wrong ideas of our “history, and culture”.

More on this in the real article, please do share your thoughts!

By Sharath with 3 comments

So, why are we here?

Yes. Long time since I came this way. Has been so busy with my masters study and exams. Now that coursework is over, that abominable bubble of emptiness has started to fill me again, giving me time to actually sit down and think. A weird feeling it is. One that fills you with tension, curiosity and uncertainty. It keeps bugging you all the time. The uncertainty, about what is in store for you. The curiosity that whether what you are doing is the right thing to be done. Most annoying of  all the tension that keeps you reminded, all through day and night about this, that asks you again and again, if everything will work out in the end. It is crushing, its excruciating, like a heavy load upon your chest that is suffocating you every minute. The root of all this is the fact that, a cause, a purpose for life is lacking or is unclear and undecided upon. Sometimes you think of how small you are in front of this vastness, this whole humanity. How much of all this can you understand and assimilate, if at all see in your lifetime that itself is just a speck.  Can all your lifetimes work make any change to the fabric of society?  If not, then why set out on something that is so tiresome and challenging.  But on the other hand, you don't want to end up repeating the same cycle of living up to the expectations of others, society, parents and friends, and then when you have  almost run out of time, start repeating the same old thing that your parents did. Get married, raise children, grow old, and then one cold morning....

So, what is it that keeps life interesting? What is that one thing in life, that will keep you going? What is that thing which is worth giving your everything for? You know this must have been answered a long time back, but you were swept away by the flow, the flood of advises and opinions and sounds that kept drowning your inside voice. You never heard yourself. But one fine day, which happens to be your birth day, you will remember with a shock that you have turned old by one more long year; and yet there you stand somewhere, lost and disoriented, haplessly trying to be good at everything, but not knowing the very thing you are looking for... As of now, this is what is churning my mind; so much  that you lose all taste and desires. I do not know if this is the beginning of something new, is it for good or bad. But I guess it is something I should and will, go through. I shall keep updating, as I feel I am not alone in this ;)

By Sharath with 2 comments

The Lord of the Rings: an allegory of the PhD?

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Characters in this satire are purely fictional. No infringement of copyrights intended.
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The story starts with Frodo: a young hobbit, quite bright, a bit dissatisfied with 

what he's learnt so far and with his mates back home who just want to get jobs 

and settle down and drink beer. He's also very much in awe of his tutor and 

mentor, the very senior professor Gandalf, so when Gandalf suggests he take on 

a short project for him (carrying the Ring to Rivendell), he agrees. Frodo very 

quickly encounters the shadowy forces of fear and despair which will haunt the 

rest of his journey and leave permanent scars on his psyche, but he also makes 

some useful friends. In particular, he spends an evening down at the pub with 

Aragorn, who has been wandering the world for many years as Gandalf's postdoc 

and becomes Frodo's adviser when Gandalf isn't around. 

After Frodo has completed his first project, Gandalf (along with head of 

department Elrond) proposes that the work should be extended. He assembles a 

large research group, including visiting students Gimli and Legolas, the foreign 

postdoc Boromir,and several of Frodo's own friends from his undergraduate days. 

Frodo agrees to tackle this larger project, though he has mixed feelings about it. 

("'I will take the Ring', he said, 'although I do not know why.'") 

Very rapidly, things go wrong. First, Gandalf disappears and has no more 

interaction with Frodo until everything is over. (Frodo assumes his supervisor is 

dead: in fact, he's simply found a more interesting topic and is working on that 

instead.) At his first international conference in Lorien, Frodo is cross-examined 

terrifyingly by Galadriel and betrayed by Boromir, who is anxious to take the credit 

for the work himself. Frodo cuts himself off from the rest of his team: from now on, 

he will only discuss his work with Sam, an old friend who doesn't really understand 

what it's all about, but in any case is prepared to give Frodo credit for being rather 

cleverer than he is. Then he sets out towards Mordor. 

The last and darkest period of Frodo's journey clearly represents the writing-up 

stage, as he struggles towards Mount Doom (submission), finding his burden 

growing heavier and heavier yet more and more a part of himself; more and more 

terrified of failure; plagued by the figure of Gollum, the student who carried the 

Ring before him but never wrote up and still hangs around as a burnt-out, jealous 

shadow; talking less and less even to Sam. When he submits the Ring to the fire, 

it is in desperate confusion rather than with confidence, and for a while the world 

seems empty. 

Eventually it is over: the Ring is gone, everyone congratulates him, and for a few 

days he can convince himself that his troubles are over. But there is one more 

obstacle to overcome: months later, back in the Shire, he must confront the 

external examiner Saruman, an old enemy of Gandalf, who seeks to humiliate and 

destroy his rival's protege. With the help of his friends and colleagues, Frodo 

passes through this ordeal, but discovers at the end that victory has no value left 

for him. While his friends return to settling down and finding jobs and starting 

families, Frodo remains in limbo; finally, along with Gandalf, Elrond and many 

others, he joins the brain drain across the Western ocean to the new land beyond.

+Jomon John +sujith samuel +Aswin R 

Author: Unknown
Source: Danny Yee’s Humour Collection
http://danny.oz.au/danny/humour/index.html

By Sharath with No comments

Knowledge is to be shared; not horded. Tribute to Aaron Swartz.

After reading the following article by late Aaron Swartz, I had this thought. Lot of us doing our higher ed has access to many peer reviewed journals, and after what the world of which we are a part, did to this wonderful person, his ideas shall only gain strength. I believe sharing knowledge is never a crime, rather its everybody's duty. Hence it would be great if everyone of us could help share the access to those who actually need the information for study and creative purposes.

"Guerilla Open Access Manifesto 

Information is power. But like all power, there are those who want to keep it for
themselves. The world's entire scientific and cultural heritage, published over  centuries in books and journals, is increasingly being digitized and locked up bya handful of private corporations. Want to read the papers featuring the most famous results of the sciences? You'll need to send enormous amounts to publishers like Reed Elsevier. 

There are those struggling to change this. The Open Access Movement has fought 
valiantly to ensure that scientists do not sign their copyrights away but instead ensure their work is published on the Internet, under terms that allow anyone to access it. But even under the best scenarios, their work will only apply to things published in the future. Everything up until now will have been lost. 

That is too high a price to pay. Forcing academics to pay money to read the work of their colleagues? Scanning entire libraries but only allowing the folks at Google to read them? Providing scientific articles to those at elite universities in the First World, but not to children in the Global South? It's outrageous and unacceptable. 

"I agree," many say, "but what can we do? The companies hold the copyrights, they
make enormous amounts of money by charging for access, and it's perfectly legal— 
there's nothing we can do to stop them." But there is something we can, something that's already being done: we can fight back. 

Those with access to these resources — students, librarians, scientists — you have been given a privilege. You get to feed at this banquet of knowledge while the rest of the world is locked out. But you need not — indeed, morally, you cannot —keep this privilege for yourselves. You have a duty to share it with the world. And you have: trading passwords with colleagues, filling download requests for friends. 

Meanwhile, those who have been locked out are not standing idly by. You have been
sneaking through holes and climbing over fences, liberating the information locked up by the publishers and sharing them with your friends. 
But all of this action goes on in the dark, hidden underground. It's called stealing or piracy, as if sharing a wealth of knowledge were the moral equivalent of plundering a ship and murdering its crew. But sharing isn't immoral — it's a moral imperative. Only those blinded by greed would refuse to let a friend make a copy. 
Large corporations, of course, are blinded by greed. The laws under which they operate require it — their shareholders would revolt at anything less. And the politicians they have bought off back them, passing laws giving them the exclusive power to decide who can make copies. 

There is no justice in following unjust laws. It's time to come into the light and, in the grand tradition of civil disobedience, declare our opposition to this private theft of public culture. 

We need to take information, wherever it is stored, make our copies and share them with the world. We need to take stuff that's out of copyright and add it to the archive. We need to buy secret databases and put them on the Web. We need to download scientific journals and upload them to file sharing networks. We need to fight for Guerilla Open Access. 

With enough of us, around the world, we'll not just send a strong message opposing the privatization of knowledge — we'll make it a thing of the past. Will you join us? 

Aaron Swartz 

July 2008, Eremo, Italy"
Rest in Peace Aaron

(November 8, 1986 - January 11, 2013)

By Sharath with No comments

German PhD/ Testing Camscanner.

It has been a long time since my last post. phew.... how time flies!
One frikking semester went just like that!
I found a brochure from the German Academic service center (DAAD) lying around, regarding PhD in Germany. Since I remember many of my friends back home asking me about opportunities, and found lots of info on this thing, and I recently installed camscanner on my phone, but had not got a chance to use it properly, I decided to make the doc digital using camscanner :D So here it is, you can download it from my dropbox public folder. Warning: It comes with a stupid pic of mine at the end! +Jomon John I think the information will be useful for anyone with a bachelors degree.

EARNING A DOCTORATE IN GERMANY

By Sharath with No comments

Photolithography Processing.

Photolithography Processing.

Photolithography is the process of transferring geometric shapes on a mask to the surface of a silicon wafer.

Photolithography Processing: Basic concepts for photolithography, process overview, negative and positive lithography, critical dimension generations, light spectrum, resolution and process latitude, Eight basic steps of photolithography process.

In spite of advances in photolithography, processor clockspeeds remained largely constant from 2000 to 2006, because clock speed of memory was maximum 666 MHz. Hence the industry has adopted multitasking and multi core architectures.

Types of lithography.

UV Lithography: This is usually referred to as photolithography itself. UV light source is used.

Immersion UV Lithography: Optical immersion lithography utilizes liquids with refractive indices >1 (the index of air) below the last lens element to enhance numerical aperture and resolution, enabling sub-40-nm feature patterning. This shift from conventional dry optical lithography introduces numerous challenges requiring innovations in materials at all imaging stack levels.

X ray Lithography: It uses X-rays to transfer a geometric pattern from a mask to a light-sensitive chemical photo resist, or simply "resist," on the substrate. A series of chemical treatments then engraves the produced pattern into the material underneath the photo resist.

Electron Beam Lithography: The primary advantage of electron beam lithography is that it is one of the ways to beat the diffraction limit of light and make features in the nanometre regime. This form of maskless lithography has found wide usage in photo mask-making used in photolithography, low-volume production of semiconductor components, and research & development.

Ion Beam Lithography:
Ion beam lithography, or ion projection lithography, is similar to Electron beam lithography, but uses much heavier charged particles, ions. Ion beam lithography has been found to be useful for transferring high-fidelity patterns on three-dimensional surfaces. Ion beam lithography offers higher resolution patterning than UV, X-ray, or electron beam lithography because these heavier particles have more momentum. This gives the ion beam a smaller wavelength than even an e-beam and therefore almost no diffraction. The momentum also reduces scattering in the target and in any residual gas. There is also a reduced potential radiation effect to sensitive underlying structures compared to x-ray and e-beam lithography.
Nanoimprint lithography is a method of fabricating nanometer scale patterns. It is a simple nanolithography process with low cost, high throughput and high resolution. It creates patterns by mechanical deformation of imprint resist and subsequent processes. The imprint resist is typically a monomer or polymer formulation that is cured by heat or UV light during the imprinting. Adhesion between the resist and the template is controlled to allow proper release.
Scanning probe lithography describe a set of lithographic methods, in which a microscopic or nanoscopic stylus is moved mechanically across a surface to form a pattern.
This type of method can be split in two different groups:

Constructive - In which the patterning is done by directly transferring chemical species to the surface (Dip Pen Nanolithography)

Destructive - In which the patterning is done by providing the substrate with energy (Either mechanical, or thermal, photonic, ionic, electronic, Xrays, and so on and so forth) to physically, chemically, electronically deform the substrate's surface.

Main parameters of lithography.

 Resolution
 Throughput (wafers per hour)

 Registration (alignment accuracy)

Three Basic UV Exposure Methods

Contact Printing

In contact printing, the resist-coated silicon wafer is brought into physical contact with the glass photomask. The wafer is held on a vacuum chuck, and the whole assembly rises until the wafer and mask contact each other. The photoresist is exposed with UV light while the wafer is in contact position with the mask. Because of the contact between the resist and mask, very high resolution is possible in contact printing (e.g. 1-micron features in 0.5 microns of positive resist). The problem with contact printing is that debris, trapped between the resist and the mask, can damage the mask and cause defects in the pattern.

Proximity Printing

The proximity exposure method is similar to contact printing except that a small gap, 10 to 25 microns wide, is maintained between the wafer and the mask during exposure. This gap minimizes (but may not eliminate) mask damage. Approximately 2- to 4-micron resolution is possible with proximity printing.

Projection Printing

Projection printing, avoids mask damage entirely. An image of the patterns on the mask is projected onto the resist-coated wafer, which is many centimeters away. In order to achieve high resolution, only a small portion of the mask is imaged. This small image field is scanned or stepped over the surface of the wafer. Projection printers that step the mask image over the wafer surface are called step-and-repeat systems. Step-and-repeat projection printers are capable of approximately 1-micron resolution. They print » 50 wafers/hour and cost $10M -20M.

The reticle and photomasks are the two things used to form the pattern on the substrate.

Feature Size is usually roughly half of the resolution. The minimum feature size is called Critical Dimension.

Registration: how accurately patterns on successive masks can be aligned (or overlaid) with respect to previously defined patterns.

Throughput: number of wafers that can be exposed/unit time for a given mask level.

Until now, most used portion of spectrum is the UV spectrum. This is due to the cheap and ready availability of UV sources.

UV spectrum is 10 nm to 400 nm.

Mercury Vapour Lamp Source: g line =436 nm

i line= 365nm

Deep UV (DUV) : Current state-of-the-art photolithography tools use deep ultraviolet (DUV) light from excimer lasers with wavelengths of 248 and 193 nm (the dominant lithography technology today is thus also called "excimer laser lithography"), which allow minimum feature sizes down to 50 nm. Excimer laser lithography has thus played a critical role in the continued advance of the so-called Moore’s Law for the last 20 years.

Alignment:

n  Mask for each layer must be aligned to previous layer patterns

n  For a minimum feature size ~ 1 mm => alignment tolerance should be +/- 0.2 mm

n  To align, wafer is held on vacuum chuck and moved around using an xyz stage

Overlay Budget: How much misalignment is allowed.

Positive and Negative Photoresists.

There are two types of photoresist: positive and negative. For positive resists, the resist is exposed with UV light wherever the underlying material is to be removed. In these resists, exposure to the UV light changes the chemical structure of the resist so that it becomes more soluble in the developer. The exposed resist is then washed away by the developer solution, leaving windows of the bare underlying material. In other words, "whatever shows, goes." The mask, therefore, contains an exact copy of the pattern which is to remain on the wafer.

Negative resists behave in just the opposite manner. Exposure to the UV light causes the negative resist to become polymerized, and more difficult to dissolve. Therefore, the negative resist remains on the surface wherever it is exposed, and the developer solution removes only the unexposed portions. Masks used for negative photoresists, therefore, contain the inverse (or photographic "negative") of the pattern to be transferred. The figure below shows the pattern differences generated from the use of positive and negative resist.

CLEAR FIELD/DARK FIELD

Masks where most of the Cr remains and the features of interest are defined by regions where the Cr is removed are referred to as positive tone or dark field masks.  Masks where most of the Cr is removed and the features are defined by regions where the Cr remains are referred to as negative tone or clear field masks.  This is illustrated in the following figure.

Eight Steps of Lithography:

Vapour Priming: Cleaning the sample to remove dirt dust and residual PR. If water is present on top, it causes poor photoresist adhesion. So we bake wafer at 200-250C (dehydration baking).

Another objective of Vapor Priming is to make the inorganic Silicon surface more adhesive to the organic PR being used.

1)Wafer surface is first cleaned to remove dirt dust and residual PR.

2)Pre bake at 200-250 C to evaporate off excess water. Complete moisture removal is quite impossible due to the strong –OH bond. So, after pre baking, the oxide will form bonds with moisture in the air.

3) Then we prime the wafer with HMDA –HexaMethylDiSilazane. HMDA is dispensed onto the wafer held by vacuum chuck. The excess liquid is then spun off.

The HMDS primer will bond with the –OH groups to seal out any moisture. The Si(CH3)3 molecules are compatible with the PR, creating adhesion between the two.

2. Spin Coating: The photoresist is then applied to the vapour primed wafer. The wafer is held on chuck and the nozzle applies ~5ml phototresist to the centre while chuck rotates at slow speeds of 500 rpm.

This speed is then ramped up to 3000-5000 rpm. Resist layer thickness depends on viscosity of resist and is inversely proportional to the squareroot of the spin speed, t ∝ 1/√ω2.

Edge Bead: The PR may sometimes form a cusp at the wafer edge or may even spil ot to the other side of the wafer. The edge beads can be removed at the end of spin coating at reduced spin speed. A jet of solvent suitable for the type of photoresist is directed to the top 2-5mm edge of the wafer to dissolve the front surface edge bead and another jet of solvent is directed to the backside of the wafer to remove the backside edge bead.

3. Soft Baking: Soft-baking is the step during which almost all of the solvents are removed from the photoresist coating. Soft-baking plays a very critical role in photo-imaging. The photoresist coatings become photosensitive, or imageable, only after softbaking. Improves Photoresist-to-Wafer Adhesion and Promotes Resist Uniformity on Wafer. Oversoft-baking will degrade the photosensitivity of resists by either reducing the developer solubility or actually destroying a portion of the sensitizer. Undersoft-baking will prevent light from reaching the sensitizer. Positive resists are incompletely exposed if considerable solvent remains in the coating. This undersoft-baked positive resists is then readily attacked by the developer in both exposed and unexposed areas, causing less etching resistance.

Typical Bake Temperatures are 90 to 100°C for about 30 Seconds, On a Hot Plate, Followed by Cooling Step on Cold Plate

4. Alignment and Expose: One of the most important steps in the photolithography process is mask alignment. A mask or "photomask" is a square glass plate with a patterned emulsion of metal film on one side. The mask is aligned with the wafer, so that the pattern can be transferred onto the wafer surface. Each mask after the first one must be aligned to the previous pattern.

After prebaking, the photoresist is exposed to a pattern of intense light. The exposure to light causes a chemical change that allows some of the photoresist to be removed by a special solution, called "developer" by analogy with photographic developer. Positive photoresist, the most common type, becomes soluble in the developer when exposed; with negative photoresist, unexposed regions are soluble in the developer.

The areas that are exposed to the UV light will undergo a chemical reaction. The water in this reaction is obtained from humidity in the air. If the air is not humid enough, the remaining carbon bond will bond with the resin, creating an insoluble material.

5. Post Expose Bake:

In this the wafer is heated to Typical Temperatures 100 to 110°C on a hot plate immediately after Exposure . In chemically amplified resists, the PEB catalytically performs and completes the photo reaction initiated during exposure. A PEB performed near the softening point of the photo resist reduces mechanical stress formed during softbake and exposure of especially thick resist films due to the expanding nitrogen and therefore improves resist adhesion and reduces underetching in subsequent wet chemical etching. However, a certain delay between exposure and PEB is required to outgas N₂. Otherwise, during PEB the N₂ in the resist will expand and increase mechanical stress in the film!

The PEB promotes the thermally activated diffusion of carboxylic acid formed during exposure from the photo active compound. This diffusion step smoothens the spatial periodic pattern of carboxylic acid having their origin in standing light waves during monochromatic exposure especially in case of highly reflective substrates. These patterns otherwise would transfer to the resist profile

6. Develop: Soluble areas of photoresist are dissolved by developer chemical. Commonly used chemical for positive resists is Tetramethylammonium hydroxide. Tetramethylammonium hydroxide (TMAH or TMAOH) is a quaternary ammonium salt with the molecular formula [(CH₃)₄N]⁺[OH]^-, and is highly effective in stripping photoresist.

7.Hard-Baking

Hard-baking is the final step in the photolithographic process. This step is necessary in order to harden the photoresist and improve adhesion of the photoresist to the wafer surface. The hardbake sometimes performed after development intends to increase the thermal, chemical, and physical stability of developed resist structures for subsequent processes (e.g. electroplating, wet-chemical and dry-chemical etching). Evaporates Remaining Solvent and Improve Resist-to-Wafer Adhesion .

8. Develop Inspect: Inspect the wafers for defects, and redo if needed.

By Sharath with No comments