Figure 1 below shows a schematic of an ideal mosc device. Ideal metalsemiconductor junction outside equilib rium reading assignment. Schottky barrier models 1 the schottkymott model according to schottky and mott 1938 the height of the barrier between a metal and an ntype semiconductor is given by q. Metal semiconductor interfaces rectifying schottky junction nonrectifying ohmic contacts 4. For an ideal mosc structure, some properties should. Metal semiconductor contact anchit biswas techno india,saltlake 2. Importance of metal semiconductor contacts is due to l ohmic metal semiconductor junctions e. For example, good ohmic contacts are essential for achieving excellent electrical characteristics of a semiconductor device, while schottky i. Metalsemiconductor junction an overview sciencedirect topics. Parasuraman,department of metallurgy and material science,iit madras. Written for semiconductor technologists and physicists.
The model covers the entire range from schottky to ohmic contacts and fits well with experimental ivcharacteristics of intermediately doped silicon. At the same time, such contacts cannot be assumed to have a resistance as low as that of two connected metals. Metal semiconductor contacts are an obvious component of any semiconductor device. The term metalsilicon contact includes silicidesi contacts. As the name implies, the ms junction is that a metal and a semiconductor material are contacted closely.
This second edition brings a greatly expanded treatment of the physics of schottkybarrier formation to its comprehensive discussion of modern semiconductor technology. Metal semiconductor contacts and devices 97801223417. Metalsemiconductor contacts, leds, lasers, some solar cells, photodetectors. Importance of metal semiconductor contacts is due to 1 ohmic metal semiconductor junctions e. Metalsemiconductor contacts monographs in electrical and electronic engineering. To improve the contacts, the interface formed between metal and semiconductor during contact deposition must be better understood. Metalsemiconductor contacts are an obvious component of any semiconductor device. Ideal metalsemiconductor contacts but the point of adding contacts was to apply fields, lets look at this m s metal semiconductor ntype apply positive bias, v v e v e c e i e fs current e fm this lowers e fm below e fs and reduces the barrier seen by electrons.
Most metalsemiconductor contacts are annealed or alloyed after the initial deposition of the metal in an effort to further improve the contact resistivity. Chapter 3 260 ece 615 semiconductor devices i winter 2019 john labram announcements midterm i will return graded midterm examinations on thursday 14th february. The metal oxide semiconductor field effect transistor mosfet is one of the cornerstones of modern semiconductor technology. Gold contacts are often formed by electroless deposition however this forms a complex interface. Metal semiconductor interfaces rectifying schottky junction nonrectifying ohmic contacts 3. Ohmic contact ms junction with large js v small linearize iv characteristics. In this module on metal semiconductor contacts, we will cover the following topics. B is significantly higher than the thermal energy kt, the semiconductor is depleted near the metal and behaves as a schottky barrier. Process engineers, device physicists, circuit designers, and students of this discipline will find the book very useful. Thus, optimizing the contacts between 2d semiconductors and metal electrodes is an important technological challenge. Ohmic contacts common techniques to make ohmic contacts choose metal so that its work function fmetal is close to that of semiconductors fsemi thermal ionic insert thin layer of narrow bandgap material between metal and semiconductor increase the doping level near the semiconductor surface as high as possible tunneling assisted. Characterization of the metalsemiconductor interface of. Figure 1 shows the energy band diagram after the contact is made.
Metal semiconductor contacts and devices by simon s. Purchase metal semiconductor contacts and devices, volume 1st edition. In particular, a large mismatch between the fermi energy of the metal and semiconductor can result is a highresistance rectifying contact. Doitpoms tlp library introduction to semiconductors metal. Electrical, chemical, morphological, and other properties at metalsemiconductor interfaces often control or limit overall device performance. Will be online after lecture 11 tuesday 19th february. Topics covered include the factors that determine the height of the schottky barrier, its currentvoltage characteristics, and its capacitance. Lecture 17 metalsemiconductor junction march 14, 2007 contents. Save up to 80% by choosing the etextbook option for isbn. The insulating film contains stationary charges of sign opposite to the sign of the conductivity of the semiconductor whereby image charges are. The general structure is a lightly doped ptype substrate, into which two regions, the source and the drain, both of heavily doped ntype semiconductor have been embedded. Department of electronics engineering, national chiao tung university, hsinchu, taiwan.
Basically, there are two types of ms contacts that are widely used in semiconductor devices. The physics and technology of metal semiconductor interfaces are keypoints in the development of silicon carbide sic based devices. A nonrectifying contact whose relationship between current and voltage has a low interfacial contact resistance r c, and is preferably linear, is referred to as an ohmic contact. Chapter 4 metalsemiconductor contacts and semiconductor. It is well known that the quality of metalsemiconductor contacts plays an important role in the performance of various semiconductor devices and integrated circuits.
Chapter 5 metalsemiconductor compound contacts to nanowire. Unlimited viewing of the articlechapter pdf and any associated supplements and figures. Metal semiconductor contacts and devices, volume 1st. Metalsemiconductor ohmic contacts rcsd r dp rext rov x y 0 sidewall gate silicide nextx novy year 1997 1999 2003 2006 2009 2012 min feature size 0. A metal semiconductor contacts without interface states. Metaloxidesemiconductor mos fundamentals engineering. Although in the last decade, the metal to 4hsic contacts. Introduction to metal semiconductor contacts sze and ng. Doitpoms tlp library introduction to semiconductors.
Several strategies, such as phase engineering to create lat eral metalsemiconductormetal heterojunctions 14, formation of. A high doping narrows the depletion region and increases the probability for tunneling significantly. The small barrier that exists for electron flow from metal to the semiconductor, but vanishes when. For example, good ohmic contacts are essential for achieving excellent performance of a semiconductor device, while schottky i. Introduction to semiconductors and semiconductor devices a background equalization lecture reading. Lecture 1 introduction to semiconductors and semiconductor. May 16, 2018 the junctions formed at the contact between metallic electrodes and semiconductor materials are crucial components of electronic and optoelectronic devices 1. Metalsemiconductor interfaces rectifying schottky junction nonrectifying ohmic contacts 4. Introduction metal semiconductor junctions a wide range of metals, such as silver ag, gold au, copper cu, aluminum al and alloys are used to make electrical contacts to semiconductors. The effect of interface states on the barrier heights of metal semiconductor contacts was first analyzed by cowley and sze 33. A monographs in electrical and electronic engineering rhoderick, e. Semiconductor materials are a subclass of materials distinguished by the existence of a range of disallowed. Metalsemiconductor contacts serve as active or passive components in all semiconductor electronic devices such as diodes and fieldeffect transistors. The term metal silicon contact includes silicidesi contacts.
Metalsemiconductors contacts engineering libretexts. Characterization of the metalsemiconductor interface of gold. Topics covered include the currentvoltage relationship, the capacitance of rectifying contacts, and practical methods of fabricating contacts. Challenge of applying ohmic contacts to gallium arsenide. A short discussion is also given of practical contacts and their application in semiconductor technology, and a comparison is made with pn junctions. For a sufficiently large schottky barrier height, where.
Electronic materials, devices, and fabrication by prof s. This section describes each of these contacts as well as an analysis of the contact resistance between a metal and a thin semiconductor layer. Metalsemiconductor junctions barrier basics shorted metal and semiconductor in physical contact as the distance between the metal and semiconductor decreases to zero, the depletion region grows qf m e f qc s e e c qf b qf m qc s v the final depletion region width is that needed to support a potential change equal to the builtin. Metal semiconductor ohmic contacts rcsd r dp rext rov x y 0 sidewall gate silicide nextx novy year 1997 1999 2003 2006 2009 2012 min feature size 0. The physics of carrier transport across the metal semiconductor junction renders metal contacts either rectifying a. Introduction usually, in device simulation the physical system metal semiconductor ms interface. Metallic contact between mos2 and ni via au nanoglue cover page pdf available in small 1422 may 2018 with 152 reads how we measure reads.
Metalsemiconductor ohmic contacts stanford university. Ohmic contacts to semiconductor surfaces are fabricated by a process which includes the formation of an adherent, uniform insulating film at the interface between the semiconductor surface and the metallization layer. Device structure, equilibrium energy band diagram, electrostatic analysis, energy band diagram under bias, capacitancevoltage characteristics, image charge, dependence of barrier height on electric field, energy band diagram of schottky contact under bias, thermionic emission current, ohmic contact by heavy. Gold has a work function closely matching that of high resistivity cdznte and is a popular choice of contact metal. Metalsemiconductor contacts fermi level pinning is the lack of barrier height modulation with metal work function due to either large density of intrinsic states. Metalsemiconductor contacts monographs in electrical and. E i e v e c e i b e f when the materials are brought into contact with one another, they are not in equilibrium e fs. The metal semiconductor ms contact is an important component in the performance of most semiconductor devices in the solid state. Metalsemiconductor contacts monographs in electrical and electronic engineering rhoderick, e.
Chapter 4 metalsemiconductor contacts and semiconductorsemiconductor heterojunctions 4. Current begins to flow from the semiconductor to the metal. The physics and technology of metalsemiconductor interfaces are keypoints in the development of silicon carbide sic based devices. Metalsemiconductor interfaces rectifying schottky junction nonrectifying ohmic contacts 3. Whether a given metalsemiconductor junction is an ohmic contact or a schottky barrier depends on the schottky barrier height. Ideal metal semiconductor contacts now lets bring the metal and semiconductor together e 0 m s metal semiconductor ntype s e c e fs e v e fm m. The principle of forming different types of the metalsemiconductor contact is the mismatch of the fermi energy between metal and semiconductor material, which is due to the difference in work functions. Device structure, equilibrium energy band diagram, electrostatic analysis, energy band diagram under bias, capacitancevoltage characteristics, image charge, dependence of barrier height on electric field, energy band diagram of schottky contact under bias, thermionic emission current, ohmic. Us3983264a metalsemiconductor ohmic contacts and methods. The principle of forming different types of the metal semiconductor contact is the mismatch of the fermi energy between metal and semiconductor material, which is due to the difference in work functions. Importance of metalsemiconductor contacts is due to l ohmic metalsemiconductor junctions e. It is well known that the quality of metal semiconductor contacts plays an important role in the performance of various semiconductor devices and integrated circuits. Introduction formation of barrier current transport processes measurement of barrier height device structures ohmic contact. Analytical model of the metalsemiconductor contact for.