An Indian Patent – A NOVEL ABRASIVE FREE CHEMICAL MECHANICAL PLANARIZATION (AFCMP) OF NON-POLAR AND SEMI POLAR III-V NITRIDE SURFACES has been granted to Dr. Dibakar Das and his team members from University of Hyderabad (UoH) and Tata Institute of Fundamental Research (TIFR), Mumbai for a period of Twenty years.
Dr. Dibakar Das
III-V nitride semiconductors (such as GaN, AlN, AlGaN, InN, InP, InGaN etc), in particular, are ideally suited for a wide range of electronic and optoelectronic applications especially for visible and UV-light emitting devices (LED) and for high-temperature and high-frequency applications in unfriendly environment. Nitride semiconductors have mostly been used in optoelectronics such as blue/green LEDs for various display applications. Recently it has been used for RF and microwave power electronics for applications in wireless communications. III-V nitride semiconductors are formed mostly in wurtzite crystal structure, where the polar planes, with Miller indices (0001 or 000-1), are formed by one type of atoms, such as Ga or N in GaN, for example. Non-polar planes, with Miller indices (11-20, 10-10 etc), which are perpendicular to the polar planes and semi-polar planes, with Miller indices (11-22, 10-11 etc), which are inclined to the polar plane at an angle q < 900, contain both type of atoms, Ga and N in GaN, for example. III-V nitrides with non-polar orientation, such as (11-20) and semi-polar orientation, such as (11-22) are better alternative than polar orientations, such as (0001) or (000-1) for laser diode, visible and ultra-violet LEDs and high power electronic devices applications because of the absence of or large reduction in built-in electric field resulting from spontaneous and piezoelectric polarization. Device applications require a smooth and flat semiconductor surface. However, most non-polar and semi-polar epitaxial layers are grown heteroepitaxially on miscut sapphire substrates, where the anisotropic nature of the growth surface results in a rough surface morphology. Growth of high quality homoepitaxial layer on the bulk crystal is also challenging because of the presence of damaged sub-surface layer in the final mechanically-polished bulk wafer after grinding and lapping. Therefore, very smooth and atomically flat surface (rms roughness £ 0.5 nm) with no sub-surface damage is a pre-requisite for growth of high quality epitaxial device layer. Removal of the surface defects and improvement in surface roughness (rms roughness < 0.5 nm) is done by a process called chemical mechanical planarization (CMP). The current invention on abrasive free chemical mechanical planarization (AFCMP) technology is a significant step towards development of high quality device layer for fabrication of electronic devices based on III-V nitride semiconductors.
Inventors:
Dibakar Das, S Vijayalakshmi, Khushnuma Asghar (UoH)
Arnab Bhattacharya, A Azizur Rahaman, Nirupan Hatui (TIFR, Mumbai)
Indian Patent No. : 396483 granted for 20 years from the 1st day of August 2013 in accordance with the provisions of the Patents Act, 1970.
About University of Hyderabad
The University of Hyderabad is an institute of post-graduate teaching and research. The school was established by an act of the Parliament of India in 1974 as a Central University. Over the years, it has emerged as a top ranking institute of higher education and research in India. The university also offers courses under distance learning programs. The university is a member of the ‘Association of Indian Universities’ (AIU), the ‘Association of Commonwealth Universities’ (ACU) and ‘International Council for Distance Education’. An Academic Staff College has been functioning on the university campus since 1988 under the UGC scheme for improving the standards of teaching in colleges and universities. The college organizes orientation and refresher courses for college and university teachers.
For more information, visit: University Of Hyderabad