GK: Physics -Importans of Laws and Principles– Terminology
- When a body is immersed either wholly or partially in a fluid at rest, the apparent loss of weight suffered by it is equal to the weight of the fluid displaced by it.
- Equal volumes of all gases under the same conditions of temperature and pressure contain equal number of molecules.
BLACK BODY RADIATION:
- A black body absorbs heat or radiates heat more quickly than any other body.
- It increases with the increase of pressure. The presence of impurities also raises the boiling point of a liquid.
CENTRE OF GRAVITY:
- A body will remain at rest only if the vertical line through the centres of gravity passes through the base of support of the body.
- The force between the two electric charges reduces to a quarter of its former value when the distance between them is doubled.
FARADAY'S LAWS OF ELECTROLYSIS:
- The amount of chemical change during electrolysis is proportional to the charge passed.
- The masses of substances liberated or deposited by the same quantity of electric charge are proportional to their chemical equivalents.
LAW OF CONSERVATION OF MATTER:
- In chemical changes, matter is neither created nor destroyed. The sum total of the masses of all the products of a chemical change is exactly equal to the sum total of the substances from which these products have been formed.
LAWS OF THERMODYNAMICS:
- The amount of heat given to a system is equal to the sum of the increase in the internal energy of the system and the external work done.
- It is impossible to construct a continuous self-acting machine that can pump heat energy from a body at lower temperature to a body at higher temperature.
- When an electric current is induced by a change in magnetic field, the induced current is always in such a direction that its magnetic field opposes the change of field which causes the induction.
MASS - ENERGY EQUATION:
- E = mc2, where E = quantity of energy released from the annihilation of matter of mass 'm', c = velocity of light. It implies that mass and energy are interchangeable.
NEWTON'S LAW OF COOLING:
- The rate at which a body cools or loses its heat to its surroundings is proportional to the excess of mean temperature of the body over that of the surroundings, provided this temperature excess is not too large.
NEWTON'S UNIVERSAL LAW OF GRAVITATION:
- Every body in the universe attracts every other body with a force, directly proportional to the product of their masses and inversely proportional to the square of the distance between them.
NEWTON'S LAWS OF MOTION:
- Everybody continues in its state of rest or of uniform motion in a straight line unless it is compelled to change that state by a force [called Law of Inertia.
- The rate of change of momentum of a moving body is proportional to the applied force and takes place in the direction of the force.
- For every action there is an equal and opposite reaction.
- The amount of current flowing in an electric circuit is governed by the voltage of the battery on dynamo which powers it. In other words, the current through a conductor is directly proportional the potential difference across the conductor and inversely proportional to its resistance.
RECTILINEAR PROPAGATION OF LIGHT:
- Light travels in a straight line. Total internal reflection takes place when a ray of light tries to pass from a denser medium to a rarer medium at an angle of incidence more than the critical angle
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Recent Trends in Optical Lithography
As the device size is reduced below 100nm various advanced methods are devised to pattern such small devices. Presently in the industry 193 nm wavelength is used to pattern the devices. Limitations imposed by 193 nm lithography in patterning devices of size less than 100nm has forced the active development of 157 nm and 121 nm lithography. Liquid immersion lithography for the same 193 nm is widely used to pattern low sized device. Practical implementation of short wavelength optical lithography is challenged by the constraints of materials used and optimizing their photochemistry. A transition to the shorter wavelength requires many of the issues related to the material science to be addressed like improving the lens materials and coatings, and the development of transparent and etch resistant photo resists.
2. Lithography at 157 nm
Several changes in the projection systems, photo mask and the photo resists are required for the technology transition from 193 nm to 157 nm. The lens material used for the projection system is crystalline calcium fluoride, optical coatings are made up of fluoride thin films and high purity nitrogen is used for ambient. The quality of the crystal grown for 157 nm should be of higher quality than that of 193 nm. At the new wavelength the absorption coefficient should be less than 0.002cm-1. This requirement imposes stringent impurity levels in the crystal. The expected residual stress induced birefringence must be less than 1nm/cm and the inhomogenesities in refractive index must be less than 1ppm.
Either the crystal growth or the annealing can't reduce the intrinsic birefringence of calcium fluoride. This effect is more observed in 157 nm than in 193 nm. Lenses made up of two different crystalline orientations can overcome this problem.
Highly transparent antireflective coating is required for optical elements. At 157 nm oxide films used at higher wavelengths are too absorptive. Since fluoride films are used almost universally, their antireflective properties and long term durability to laser radiation exposure should be qualified.
The cleanliness of the purge gas plays vital role at 157 nm. In 193 nm photo induced contamination of optics due to trace contaminants in the purge gas exists. This effect worsens in shorter wavelength side.
Several absorptive materials are under investigation for attenuating phase shift photo mask. Protecting the photo mask from the particle contamination is the important issue related to photo mask in 157 nm. There is a zero tolerance for the particles falling on the photo mask. A very thin membrane, called pellicle, is used to protect the mask. The chosen pellicle materials have shown rapid degradation when pellicle is radiated with a 157 nm laser. Practically 10 % lifetime value of the pellicle must be at least 1KJ/cm2. most of the pellicles tested for 157 nm is found to be having 10% life time of only 75/cm2. This failure happened due to the process called as photochemical darkening. 
To get good quality photo resists the absorption coefficient of 157 nm photo resists must be reduced to less than or equal to 2um-1. Photo resists having a thickness of 120 nm have shown resolution of 120 nm. Absorption coefficients of less than 1um-1 have been reported recently. Incorporation of transparent inorganic nano particles in the polymer of the photo resist accomplishes two goals- increased transparency and enhanced plasma etch resistance (i.e. low etch rate), thus enabling a smaller thickness.
3. Liquid immersion lithography
In this technique higher resolution is achieved by increasing numerical aperture (NA) beyond 1 through the use of immersion liquids. From the equation R=(k1.λ)/NA it is clear that higher resolution can be achieved either by reducing λ and k1 or by increasing the refractive index of the imaging medium. If we employ a liquid of refractive index 1.4 instead of air or nitrogen then the maximum NA achievable approaches to 1.4. This enables the resolution enhancement proportional to 'n'. This can be achieved without changing the any of the established technology base like wavelength, laser, photo masks etc.
Liquid immersion lithography is implemented at deep ultraviolet wavelength of 193 and 157 nm. Availability of transparent liquids is vital to liquid immersion lithography. DI water provides very good absorption coefficient of 0.036cm-1. This enables the projection system designers to keep sufficient working distance (~1mm) of several millimeters. Presently available transparent liquid at 157 nm has an absorption coefficient of 3cm-1 requiring a working distance of less than 0.1 mm. For a better working distance reduction in absorption coefficient is necessary.
Photo resist performance is affected by interactions between the immersion liquid and the photo resist. In the absence of laser irradiation thinning of 193 nm photo resist by the liquid is less than 0.5 nm which is well within the acceptable limits. 45 nm device patterning is possible with the 193 nm liquid immersion lithography and 32 nm devices can be manufactured with the advent of 157 nm technology.
4. Lithography at 121 nm
The wavelength of 121.6 nm is also known as Lyman alpha line. This is shortly called as 121 nm. This is the shortest wavelength used in optical lithography. Vacuum based systems are not necessary for 121 nm technology compared to alternatives like Extreme ultra Violet (EUV) at 13 nm or electron beam lithography. Lithographic systems used for 157 nm technology can be engineered to 121 nm technology also because absorption coefficient of most common purge gases and atmospheric constituents are similar.
The main difference of 121 nm from the 157 nm is the use of pulsed discharge sources instead of lasers. The lack of suitable transparent optical materials is imposing difficulties in the development of 121 nm technology. Since high NA over 0.75 is required for the projection systems, the lenses used for optical systems should be of either all refractive (using only lenses) or catadioptric (a combination of lenses and mirrors). A highly transparent lens material like lithium fluoride which has high band gap is used for the manufacture of lenses.
Design of proper photo resist for the new wavelength is always a challenging job. The universally high absorption coefficient of organic polymers necessitates the use of thin layers of photo resist, approximately of thickness 25 to 35 nm. This mentioned thickness of the photo resist is three times less than the thinnest photo resist used at 157 or 193 nm. There can be setback on the development of 121 nm technologies considering the fact that lower thickness of the photo resist may not be compatible with the pattern transfer processing steps such as reactive ion etching.
A survey  of leading chip manufacturers finds that for 130 nm node 248 nm lithography is used; for 100 nm node 193 nm lithography is the choice of majority of companies. For the fabrication of 70 nm patterns 157 nm lithography is a workhorse, but several companies have shown interest in Electron Beam Lithography (EBL). For the 50 nm and bellow node there is a great degree of debate in the industry to switch over to either EBL or Extreme Ultra Violet (EUV) lithography.
However the use of optical extension techniques such as phase-shifting masks and off-axis illumination has enabled the industry to find good manufacturability solutions to extend the lifetime of optical lithography. Introduction of 157 nm lithography along with the breakthrough development of fused silica for mask materials has added more nodes to the life time of optical lithography.
As the feature size is decreasing to sub micron level, in addition to conventional optical lithography techniques, several new technologies such as x-ray, e-beam direct write (EBDW), extreme UV (EUV), electron beam lithography (EBL) and ion projection lithography (IPL) are emerging in the industry. But breakthrough researches and introduction of liquid immersion technique with new wavelength of 157 nm and 121 nm in the field of optical lithography has pushed the limits. Thus the recent trend in the optical lithography has given more breathing space for the cost sensitive semiconductor industry.
 Mordechai Rothschild, Theodore M. Bloomstein, Theodore H. Fedynyshyn, Roderick R. Kunz, Vladimir Liberman, Michael Switkes, Nikolay N. Efremow, Jr., Stephen T. Palmacci, Jan H.C. Sedlacek, Dennis E. Hardy, and Andrew Grenville, Recent Trends in Optical Lithography, Lincoln laboratory journal, volume 14, number 2, 2003
PGECET Counseling 2011: Notification for M.Tech, M.Pharmacy, M.E., M.Arch, M.Planning, Pharm.D. (P.B.) admissions for the academic year 2011-2012 through PGECET 2011, GATE 2010 and 2011 and PGEC 2011 have been announced. Candidates have to attend for the certificate verification and exercise web options as per the schedule given below. Seats allotment and detailed notification will be availble on pgecet.apsche.ac.in . Following is the counseling schedule for PGECET and PGEC candidates:
1) 9-11-2011: GPAT Candidates: Rank 1 to Last (Web options from 9th November to 11th November 2011)
2) 10-11-2011: GATE Candidates: Rank 1 to Last (Web Options from 10th November to 12th November 2011)
PGECET 2011 Counseling Schedule:
1) 15-11-2011: Rank 1 to 250 (Web options 15th - 17th 2011)
2) 16-11-2011: Rank 251 to 800 (Web options 16th - 18th 2011)
3) 17-11-2011: Rank 801 to 1800 (Web options 17th - 19th 2011)
4) 18-11-2011: Rank 1801 to 3200 (Web options 18th - 20th 2011)
5) 19-11-2011: Rank 3201 to 5000 (Web options 19th - 21st 2011)
Details of seats allotment, vacancies, colleges, reservations and other information can be obtained from the website at pgecet.apsche.ac.in
Update on 30th August 2011: PGECET 2011 Counseling will be conducted during 9th - 10th September 2011. APSCHE Chairman has announced these dates and official notification will be released in 3-4 days. Candidates can exercise web options at any helpline center for admission into M.Tech courses. Seat Allotments will be done as per the schedule given in the notification. Candidates can download allotment order from www.appgecet.nic.in OR http://www.apschepgecet.net/ . Osmania University has conducted the PGECET 2011 for the academic year 2011-12.
Andhra Pradesh State Council of Higher Education (APSCHE) will conduct PGECET Counseling 2011 for admission into M.Tech, Pharm D and M.Pharmacy Courses for the academic year 2011-12. All the seats in above courses at Govt. and Private Engineering and Pharmacy colleges will be filled through PGECET Online Counseling 2011. The Counseling process is likely to start from 29th August 2011. Candidates have to attend for certificate verification and exercise web options as part of the counseling process. Seats will be allotted as per the dates and time given in the counseling notification to be released soon. Candidates can download allotment order also from the official website of PGECET at www.appgecet.nic.in . Detailed schedule for certificate verification and web options will be update here after the release of notification.
Certificates to be produced at verification centers / helpline centers by the candidates:
1. B.Tech./ M.Sc./ MBBS/ BDS/ B.Sc. Agriculture, B.V.Sc. or other relevant Degree Marks Memos
2. Intermediate Memo cum Pass certificates
3. S.S.C. Marks list for Date of Birth proof.
4. Study Certificates from Relevant Degree to Tenth Class,
5. Residential certificate in case of non local candidate.
6. Income certificate issued by Govt. of AP after 01-01-2010
Tuition Fee per Year:
1. University Engineering and Pharmacy Colleges: M.Pharmacy Rs. 15000-25000 ; All other like ME/ M.Tech./ M. Arch./ M.Planning Rs. 15000-25000
2. University Colleges Under Self Finance: M.Pharmacy Rs. 110000; ME/ M.Tech./ M. Arch./ M.Planning Rs. 57000
3. Private Unaided Engineering and Pharmacy Colleges: Pharm D: Rs 68000 ; M.Pharmacy Rs. 110000; ME/ M.Tech./ M. Arch./ M.Planning Rs. 57000
Note: Candidates whose parental income is less than Rs.100000 will be exempted from payment of Tuition Fee subject to conditions issued by the Govt. of Andhra Pradesh time to time. Details of Helpline Centers and other info will be displayed on appgecet.nic.in
Prof. T. Krishna Rao, Director, Admissions, Osmania University, Hyderabad has announced notification for Ph.D. Eligibility Test 2011. Admission into Ph.D. / Doctoral programmes in the faculties of Arts, Commerce, Management, Social Sciences, Education, Technology, Science, Oriental Languages, Pharmacy, Engineering and Law will be through ranks in Ph.D. Eligibility Test 2011. Following are details of eligibility, selection and application procedure:
Eligibility and Qualification: Applicants should have passed the Master's degree in the concerned subject with at least 55 percent marks. SC and ST candidates need 50 percent marks. Interested candidates can obtain Application form along with ICR summary sheet and information brochure from the University Press, OU Campus, Hyderabad. Cost of application is Rs.100/-. Candidates with qualifications such as M. Phil. (through regular mode) / UGC-JRF / CSIR - UGC NET / ICMR and ICAR Research Fellowship Tests / SLET (conducted by A.P.) need not apply for Ph.D. Eligibility Test.
Sale of applications will start from from 10th November 2011. The application form and ICR sheet and information brochure can also be downloaded from Osmania University website www.osmania.ac.in/admissions. Completed application forms along with necessary enclosures and a demand draft towards registration fee should be sent to The Director, Directorate of Admissions, Near University Press, Osmania University, Hyderabad - 7. Last date for the receipt of completed applications is 9th December 2011. Last date with late fee of Rs. 100 is 17th December 2011. For more details, you can contact at Ph. No. 040-27090136.