The Fabrication Of Bipolar Junction Transistors By Diffusion Planar Lab Report

The Fabrication Of Bipolar Junction Transistors By Diffusion Planar Process - Lab Report Example The fabrication of BJT comprises of various sub-steps like RCA (Cleaning Process), Thermal Oxidation, Photolithography, Diffusion, Metallization, Alloying Process etc. The process of fabrication starts by cleaning the substrate of impurities by the RCA procedure followed by developing a layer of SiO2 on the planar surface by the process of oxidation. The wafer is then coated with an appropriate photoresist material and developed by exposure to UV through base mask (mask #1). After sufficient time of exposure, the SiO2 is removed by etching out from the region of base-diffusion followed by cleaning away the covering of the remaining photoresist coating. The P-type base i.e. Boron is diffused into this region followed by re-oxidation to develop the layer of SiO2. Next, by the process of Photolithography, the oxide layer is stripped off from the regions of collector and emitter by mask #2 and Phosphorous (N-type) is diffused on it. The entire sample is re-oxidized and once again coated with the photoresist material and developed. The substrate is then exposed to vapors of Aluminum which are allowed to condense upon it. The excess Aluminum on the substrate i.e. at non-contact regions is removed chemically by ‘lift-off’. The final step in the process is alloying of the contacts. RCA Dust, SiO2, oxides and metallic contaminants are removed. Consequently, the process has three chief procedures namely the Organic Clean, the Oxide Clean and the Ionic Clean. [5] â€Å"The RCA clean procedure should be performed immediately prior to any crucial step, especially those involving high temperatures.†[2] The RCA clean procedure consists of the following steps: Mixing of Organic, Inorganic and Oxide Stripping Solution 1. The Organic Solution is prepared by adding 1000 ml of H2O to 200 ml H2O2 and 200 ml of NH4OH. Heat the solution for 15 min at a temperature of 80  °C. [2] 2. The Ionic Solution is prepared by adding 1000 ml of H2O to 200 ml H2O2 and 200 ml of HCl. Heat the solution for 15 min at a temperature of 80  °C. [2] 3. The Oxide Stripping Solution is prepared by adding 2000 ml of H2O to the polypropylene vat. Add 40 ml of HF acid into it. [2] Bubbler Rinse Set-Up The bubbler rinse station is filled with deionized water and nitrogen is bubbled in it. [2] O rganic Clean This step removes dust, grease and other organic impurities from the substrate. The substrate is submerged in the Organic Solution for 15 min and then placed in the Bubbler Rinse Set-up for 5 min. [2]

Creativity Essay Example | Topics and Well Written Essays - 3000 words

Creativity - Essay Example However, Csikszentmihalyi suggested that young students "cannot be creative, but all creative adults were once young students' (Csikszentmihalyi, 1966:156). The entire idea of this statement by Csikszentmihalyi is dependent on the fact that young students "can show tremendous talent, but they cannot be creative because creativity involves changing a way of doing things, a way of thinking, and that in turn requires having mastered the old ways of doing/ thinking. No matter how precocious a student is this he cannot do' (1996:155). In other words Csikszentmihalyi stated that it is education that makes an individual creative. In this context it would be relevant to mention that Amabile suggested that "...creativity by individuals and teams is a starting point for innovation; the first is a necessary but not sufficient condition for the second" (Amabile et al 1996). As it is Csikszentmihalyi viewed creativity as the highest achievement of human mind as he states that "Creativity is the central source of life for several reasons. Most of the things that are interesting, important and human are the result of creativity." (1997: 1) Csikszentmihalyi's views in this context suggested that there is an attempt of invoking creativity within young students but there can be no conviction that the method proved the usher of creativity within young students of 12-16 years. It s... knowledge that they wish to acquire but they stressed on the particulars of methods and neglected creativity by keeping it aside as they implied that it is a inheriting part of the young student's mechanism. In this regard we can enumerate the ideas put forward by Emerson who suggested that "by our tempering and thwarting and too much governing he may be hindered from his end and kept out on his own" (Emerson 251) In other words Emerson believed that the students should be given enough liberty to formulate their own approach towards education or they are creative enough to formulate one. This again is an alternative view of Csikszentmihalyi's views that suggested that even if there are no direct evidence of creativity there always remains an element of attempt to be creative all along. Literature review View of Csikszentmihalyi states that "creativity results from the interaction of a system composed of three elements: a culture that contains symbolic rules, a person who brings novelty into the symbolic domain, and a field of experts who recognize and validate the innovation." (1997: 6) but in the same context Freire suggests that it " emerges through invention and reinvention, through the restless, impatient, continuing, hopeful enquiry men peruse in the world, with the world, and with each other." (Freire 319) Thus it can be enumerated that this element according to Freire is more of a reflex action rather than a formulated procedure and it can be further mentioned that this process of learning is an instrument of survival that was incorporated within us from the prehistoric era and he expects every young student to be creative. Freire stressed that the education of young students must involve their senses. He presents guidelines for creating an educational