Types of Integrated Circuits, Classification of ICs by Structure
Table of Contents
Types of Integrated Circuits
Types of integrated circuits can normally be classified under the following two topics
1). from a fabrication point of view
2). from a function or usage point of view
Classification of ICs by Structure
From a construction point of view, the types of Integrated Circuits are as follows.
i). Monolithic Integrated Circuits
ii). Thick and thin film Integrated Circuits
iii). Hybrid or multichip Integrated Circuits
Monolithic Integrated Circuits
An electronic circuit, in which all elements have been fabricated and connected above a silicon piece, is called a monolithic integrated circuit. In other words, electronic circuits which are completely fabricated on a single semiconductor material (i.e. silicon) chip are known as monolithic integrated circuits. The word monolithic has been derived from a Greek word that means a single stone. From a technical point of view, its most appropriate meaning is a single solid structure. As all circuit components (both active and passive components) are fabricated within a single crystal (which is called a wafer or substrate) of a semiconductor material (silicon), therefore it is called a monolithic IC. In other words, all circuit components in a monolithic integrated circuit are fabricated in an inseparable manner on a single piece of a silicon crystalline material. All these components are a part of this chip from the atom’s perspective, on which it is fabricated. Transistors, diodes, and other passive components are fabricated at suitable spots on or inside a substrate through the application of the epitaxial diffusion technique. Inter-connections of components are done on surface’s structure and these connections are linked with terminals via external connecting wires or leads.
Monolithic integrated circuit technology depends on silicon diffused planar process, in which the entire process (practical construction steps) is performed on the surface of a silicon slice or piece of silicon and all contacts of different components are linked with this surface. Interconnection between components is done via a metal wiring pattern of the silicon wafer’s oxide covered surface. Individual components of a given IC (i.e. transistor, diodes, resistors, capacitors, etc.) are fabricated simultaneously. In fact, similar to the manner and time required for diffusing a single transistor, all elements of a completed circuit can be diffused in approximately the same time and manner within a single wafer. In spite of few drawbacks, monolithic ICs are used on a vast scale. Remember that its preparation on a large scale is extremely beneficial from an economic perspective.
A monolithic IC is basically fabricated in a manner which is quite similar to the fabrication of a bipolar transistor. Some extra stages are included in the construction of Integrated Circuits, due to which it becomes quite complicated. The fabrication of a monolithic device starts from a round or circular semiconductor (which is normally silicon) wafer, as has been elucidated via figure 8.6 (A). The wafer is usually extremely thin and is also known as a substrate. Wafer of a semiconductor works similar to a base on which tiny integrated circuits are fabricated.
Figure 8.6 – integrated circuit construction
A large number of ICs are fabricated together on a wafer as can be seen in the figure (B). Every square in this figure depicts an IC. The number of ICs constructed on a wafer depends on size of the wafer and the size of IC itself (there may be less than 300 ICs on some of the wafers, on some others the number could be between 500-600 while on others, the number is even higher). ICs constructed on a wafer are usually similar or of the same type, therefore their size and number is also same. When all ICs are fabricated together, the wafer is then sliced into many pieces as can be seen in figure “c”. Every piece or slice is called a chip or a dice. Every chip has a complete integrated circuit on which all circuit components are mutually set in a proper and correct manner. Later on, these ICs are isolated, packed properly and tested. Some of the ICs are rejected as a result of developing some kind of physical or electrical defect during the testing.
Remember that a large of ICs can be fabricated under this method, however only few of these ICs are capable of being used, the number of which is expressed as percentage. This useable number is called “yield”. For example, if yield is 20 percent, it means that only 20 per cent of the ICs from amongst so many are in working condition. Another point which has to be kept in mind is that a monolithic IC is not produced alone, rather a large number of ICs are fabricated simultaneously and the components being used within these ICs are also simultaneously produced. In figure 8.7, basic structure of a monolithic integrated circuit has been demonstrated.
Figure 8.7 Basic monolithic IC structure
It consists of three layers containing different kind of materials. The layer located at the lower end, which is thicker compared to other two layers, is made from P type silicon, which is coated via a thin N type epitaxial (high resistivity) layer. A thin narrow layer of silicon di oxide (SiO2) exists above this structure.
All components on a diffused monolithic structure are fabricated within this thin N type region. The P region shown in the figure is not an active part of the circuit; it rather acts basically similar to a substrate, so that structure could mechanically be made more powerful or strong. Furthermore, it also performs extra task of electrical isolation or insulation among various diffused components.
Silicon di oxide’s layer performs two specific tasks. It safeguards semiconductors’ surface from external dirt and dust etc. and it also helps in selection of diffusing of various components located at the lower wafer. As every component is constructed inside N region, therefore it is essential to segregate different N regions in order to isolate various components. The following two methods are used for this purpose.
1). P-N diode isolation
2). Silicon di oxide (SiO2) isolation
The first method (i.e. P-N diode isolation has been displayed in the figure 8.8 (A). In which flow of current from one N region to another N region is prohibited by using the high resistance of a reverse biased PN junction (because both N regions have been isolated mutually via a P region substrate. Thus, N regions and P substrate assume the shape of two back to back diodes. And practically, every N region within the circuit becomes reverse biased with respect to P substrate. In this method, every N region gets insulated via other N region and substrate. Some drawbacks are found in this method due to substandard isolation resulting from a reverse biased diode and particularly junction capacitances found parallel to isolation diodes. These capacitances reduce reduces frequency response of the circuit and its switching speed.
Figure 8.8 – isolation techniques A. P-N diode isolation B. Silicon diode isolation
In other method of isolation (i.e. silicon di oxide isolation) has been represented in figure “B”. In this method, isolation is done by means of covering silicon di oxide (Sio2) layer around every N region. Under such a situation, substrate is of un-doped silicon type. This type of isolation has some advantages over first type of isolation which has been mentioned above (i.e. N diode isolation). The first advantage is that this type of isolation is defect less and perfect, because silicon di oxide is a better insulator compared to a reverse biased PN junction. Further, no capacitances exist between N region and substrate. Thus, operation on a high frequency becomes far better. However, contrary to these advantages, this type of fabrication process is quite complex. Besides due to mass production, the manufacturing cost enhances due to the extra steps involved in the isolation process of a monolithic IC. This causes an additional burden on the consumer or user of the IC.
Fabrication of Components
In a monolithic IC, transistors, diodes resistors and capacitors are normally used. In order to construct these components, impurity is added or diffused at certain spots on a semiconductor wafers (i.e. substrate), so that PN junctions could at specific spots. In figure8.9, a specific cross section of these basic monolithic components has been demonstrated. It is clear from the figure that all the four components have been fabricated inside a P type substrate or wafer. In P type substrate N type and from P type material N type and P type areas are formed, due to assistance of which four components (transistor, diodes, capacitors and resistors) are fabricated together. However, for its fabrication, process of diffusion (a popular technique in which N and P type materials (which are in gaseous form) are included in semiconductor wafer on a specific temperature, so that N or P type region could be formed respectively) has to be carried out several times. Every part of N or P type, its depth and its size has to be controlled quite accurately. First of all, layer of silicon di oxides is covered on the substrate. Then, this oxide layer is removed from the desired spots with the help of acid so that only those spots are visible, where diffusion of N type material has to be done. Then, N type material present inside the substrate is diffused from such spots so that first and largest N type part could be produced. Then a fresh layer of oxide is put on these spots and new spots are re-fabricated on this layer. P type material is now diffused on selected substrate spots, so that P type parts could be formed in the substrate. This process is repeated again until final N type part forms.
Figure 8.9 – Typical IC components A. Transistor B. Diode and capacitor C. Resistor
The NPN transistor as shown in the figure (A) is basically fabricated in a manner similar to the construction of an ordinary transistor. NPN transistor structure has been formed via consistent diffusion of impurity on the upper surface of the substrate. N type collector of the transistor has been fabricated first of all. After this, P type base and N type emitter have been fabricated. Remember that for a proper diffusion on a specific part of a substrate, first of all silicon di oxide layer is removed carefully through the application of some chemical and when the process of diffusion gets completed, upper surface from where silicon di oxide layer had been removed, SiO2 layer is coated on this part once more through which upper surface is completed. All three parts of transistor (i.e. emitter, base and collector) are expanded to the substrates’ upper surface. Metal contacts are built between different regions of the transistor. How an integrated transistor can be fabricated, its detailed clarification is as follows:
Various steps required for fabrication of a transistor have been illustrated in diagram 8.10. First of etching (removal of surficial material through the application of some chemical or cleaning SiO2 layer via acid, is called etching) is done on parts of SiO2 in order to expose epitaxial layer (figure a). After this, wafer is put in the furnace, and trivalent atoms are diffused or thrust into epitaxial layer. Concentration of trivalent atoms continues until exposed epitaxial N material converts into a P material. Thus, we get a slice of N material below SiO2 layer as reflected via the figure (b). Later on SiO2 layer is accomplished vide sprinkling oxygen once again on its surface (look at figure c). Then, a hole is made in the center of SiO2 layer via etching, due to which N epitaxial layer gets exposed or transparent (figure d). The hole made in SiO2 layer is known as a window. The N part which is visible below this window is transistor’s collector.
Figure 8.10 – steps in making a transistor
Trivalent atoms are transmitted through this window for fabricating the transistors’ base. These impurities are diffused in epitaxial layer. Due to which a P type material slice is obtained (figure e). After this, SiO2 layer is re-fabricated via passing oxygen above the wafers’ surface (figure F). For fabricating emitter of the transistor, a window is formed in SiO2 layer through etching and P type piece is exposed (figure g). After this, a tiny N slice is obtained through diffusion of pentavalent atoms in P slice (figure h) which is transistor’s emitter. Then the entire wafer is covered via passing SiO2 layer all over it (figure i). After this, three windows are made in SiO2 layer through which three small metal pieces are inserted for setting up a connection with emitter, base and collector (this action is known as metallization) as can be seen via figure 8.11. Thus, an integrated transistor is completed.
Figure 8.11 – integrated components a. transistor b. diode c. resistor
A PN junction diode displayed vide figure 8.9 (B) and or 8.11 (b), is manufactured similar to an ordinary diode. The N type part in it, which is bigger in size, is first diffused in substrate which functions as a cathode. Whereas the smaller part, which is type P, is diffused in N type part. This part works like an anode. In other words, integrated circuit diodes are fabricated by using only PN junctions of the transistor. In figure 8.9 (B), collector – base junction of the transistor has been used as a diode. Diodes’ anode is fabricated at the time of transistor’s base diffusion (remember all components on a chip are fabricated simultaneously and when prepared via diffusing the base of a transistor on the chip, diodes’ anode is also first diffused for fabricating a diode on the chip) Whereas, a diode’s cathode is fabricated alongside collector region of the diode. Metal contacts are fixed along both these regions which are brought about to the upper chip region. Such type of diode is meant for common use. Whenever high-speed switching is desired, E-B junctions of transistor are used as a diode.
Two basic methods are used for fabrication of a monolithic capacitor. In the first method, monolithic capacitors are fabricated by using the capacitances of reveres biased PN junction, as can be seen in figure 8.9 (B). As these capacitors are fabricated by using the capacitances of reverse-biased PN junction, therefore such a capacitor is also known as a junction capacitor. The capacitance value received from a junction capacitor is quite limited or low (about 100PF) and this value depends on the reverse voltage found parallel to the junction (i.e. size of depletion region reduces due to variations in bias voltage. Thus, the capacitor’s capacitance value changes as a consequence of a variation in bias voltage). Therefore, bias voltage of a correct value must always be present parallel to this device. In spite of these limitations, an advantage of this method is that a capacitor can be fabricated simultaneously via diffusion with other components.
In the second method of capacitor fabrication, metal oxide semiconductor (MOS) is used. Therefore, such type of capacitors is sometimes known as metal oxide capacitors. In this method diffused N type part functions as a capacitor’s lower plate and the silicon layer as die-electric. Capacitors’ upper layer is a kind of metal layer which is spread above silicon di oxide layer. The value of such a capacitor depends on plates area, thickness of oxide layer and die- electric constants of the layer. The capacitance value of a MOS capacitor is slightly higher as compared to the value of a junction capacitor. However, the value of these capacitors is also limited to a few hundreds’ pekoe farad. The greatest advantage of these capacitors is that they are non-polar (i.e. they can be supplied voltages of any polarity) and their leakage is low. Further, they can be operated on higher voltages as compared to junction capacitors. Practically, it is possible to fabricate capacitors of high value under this method as well, because the fabrication of large-size capacitors is necessary for the purpose of a higher capacitance value. For fabrication of large-size capacitors, more space is required (even for fabrication of 10-20 pekoe farad capacitors, the minimum space required has to be larger than a transistor)
While diodes, transistors and capacitors are being fabricated during the period of fabrication in integrated circuits, resistors are also fabricated simultaneously. Resistor is made via diffusion of an impurity inside a silicon wafer of an integrated circuit. The value of a resistor is controlled through concentration of impurity and depth of diffusion. Most of the resistors are formed at the time of diffusion of base, as can be seen in figure ©, because it is a high resistive region. In other words, in monolithic circuits, resistors are fabricated normally through the application of resistivity of a diffused area. Mostly, P type base diffusion is used for manufacturing a resistor. However, N type emitter diffusion can also be used for this purpose. Remember that resistivity in an emitter region is quite low; therefore, emitter region is also used for extremely low resistance.
A large N type space is built first for the fabrication of a resistor. Then a P type space is constructed above it. Thus, a long and thin P type material strip is made which is encompassed by an N type material (as has been displayed via the figure). This lengthy P type strip act as a resistor. Its resistance can be controlled by means of increasing or decreasing the length and breadth of this strip (resistance will increase with an increase in the length of strip whereas increasing its breath will bring about a decline in its resistance). Resistance value can also be adjusted via increasing or decreasing the quantity of P type material on a P type strip. Resistance will be low if the quantity of P type material is large and conversely it will be high if the quantity of P type material is small. Remember that more space is required for fabrication as the value of a resistor enhances. Therefore, it is difficult to fabricate resistors of higher values and higher accuracy inside an integrated circuit. However, the ratio between two resistors constructed closer to each other on the same substrate can very skillfully and carefully be controlled. In fact, ratio of resistor values between two resistors constructed on the same wafer can be sustained accurately up to 1 percent. Therefore, circuits which are constructed on an IC, they are usually designed in such a manner that the values of a resistor applied on it are expressed as per cent instead of absolute values.
It must be remembered that an inductor cannot be fabricated using IC technology. Therefore, it is attempted at the time of designing an IC that no inductor is used on it all. However, if the application of an inductor is must on the circuit, it is fixed individually outside the circuit.
As has been discussed above, all components are fabricated via a covering of silicon dioxide layer on substrate and then disposing off this layer at specific spots and diffusing N type or P type material within the substrate. Until all components have been fabricated, this process is repeated several times. In the final stage, a layer of oxide is spread on the substrate and subsequently this layer is wiped out at certain spots so that various parts of each component could become visible. After this, gold or aluminum layer is coated above oxide layer which communicates with all components on those places wherefrom oxide layer had been removed. Later on some parts of this metal layer are ended through acid and only those parts of metal layer survive which operate as a conductor and complete the circuit by connecting together various components.
Since components used in a monolithic IC are fabricated via same production technique, which is being used for construction of a bipolar transistor, thus integrated constructed in this manner are occasionally known as bipolar integrated circuits.
Remember that various components fabricated in this manner are electrically set apart or insulated from one another. Therefore, no current transmits mutually between the components despite passing of current on a circuit. However, due to being electrically insulated, the junction being used in them is PN on which current can flow just in one direction. Due to diffusion technique, every component has been fabricated within its N type region; therefore, every component is isolated from P type substrate by means of a PN junction. When circuit has been working, it biased in such a manner during that time that P type substrate is more negative as compared to other parts of the circuit. As a result, every PN junction is reverse biased and offers a great resistance. Resultantly, every component remains isolated from other component. Thus, current flowing through the circuit can pass only through its specific routes.
Formation of a Complete Monolithic IC
In figure 8.12, different phases of construction of a monolithic Integrated Circuits have been elucidated, which have been elaborated as follows:
1). First of all, different N regions are diffused on a P substrate as can be seen in the figure (A). Normally, their sizes are different, because size depends on the components, for which these have been fabricated (that’s component which is going to be fabricated in this N region, its size is set according to the size of that component). However, each and every component requires an N region.
Figure 8.12 – Integrated Circuits process steps a. isolation of N-region b. P-type basic diffusion c. N-type emitter diffusion d. contact formation e. circuit schematic
IC process steps (A). Isolation of N regions (B). P-type Base Diffusion (C). N-type emitter diffusion (D). Contact formation and interconnection (E). Circuit schematic
2). After N region, diffusion of P type base region is carried out inside N regions as can be seen via figure (B). For this silicon di oxide layer is removed from certain spots through a chemical process and thereafter, a P type impurity is inserted or diffused into N region. As far as a resistor or a diode is concerned, these have been completed at the end of this phase, however resistor still remains incomplete as its emitter region is yet to be completed.
3). in the third phase, transistor’s emitter region is fabricated. For this purpose, an N type material is diffused into P region (i.e. base) as can be seen in figure ©. Thus, transistors’ emitter also gets completed in this phase. During this process, diode and resistor are not affected at all. Because silicon dioxide layer cover on them blocks the diffusion of all sorts of impurities within the region.
4). in the final stage, which has been shown in figure (D), contacts of different components are established and then these components are connected according to a proper arrangement on the circuit via fixing a metallization pattern. In figure (E), the final circuit thus constructed, has been illustrated symbolically.
It becomes apparent from example of a completed Integrated Circuits structure as mentioned above, that all those steps which are practically being taken for fabricating an integrated circuit, are also required to be taken for construction of a transistor (except in the insulation phase). A complex circuit could have about 50 components and it can be fixed in an area of about 0.05×0.05in). A round silicon wafer, diameter of which is about 1.25”, may consist of about 350 such circuits. Thus, very large number of circuits can be prepared on a silicon wafer through using steps mentioned in the figure. When circuits are complete, these are normally tested above the wafer prior to isolating individually in the shape of chips. After testing, individual circuits on the wafer are delinked (this is normally done by scratching or cutting the wafer). After this, the individual wafers are placed on a metal or glass base. Then electrical connections are made through connecting wafer contacts via external package leads. In the end, every Integrated Circuits is enclosed in a can type case (sheath) or this package is sealed via a mold. This has been demonstrated via figure 8.13.
Figure 8.13 – a. monolithic IC in can-type enclosure b. monolithic IC in plastic package
Thick and Thin Film Integrated Circuits
The basic distinction between thick and a thin film Integrated Circuits does not rely on thickness but on the method of depositing film. Although, apparent configuration, characteristics and merits of both ICs are same, however these are different from monolithic type of ICs in several ways. These ICs are not fabricated inside a silicon wafer rather they are made on the surface of some insulating substrate e.g. glass or ceramic material. Further, only passive components e.g. resister and capacitor etc. are fabricated on insulating surface through thick and thick film technique. Active elements (transistors, diodes) are used as eternal individual discreet elements for completing the circuit. These active components are mostly prepared under monolithic process.
As discussed above, basic difference between thick and thin film technique rests on the method used for the construction of passive components and metallic conduction pattern.
Thin Film Integrated Circuit
These circuits are formed by depositing a film of some conducting material (gold or aluminum) on the surface of a glass or ceramic made substrate. Resistors and conductors are formed via variations in thickness and width of film and through using materials of different resistivity. While capacitors are fabricated by means of sandwiching an insulating film between two conducting films. Small sized inductors can also be constructed by depositing film in the form of springs. Active components (e.g. transistor and diode) are connected with such integrated circuits from outside in the form of a chip. They are connected with substrate through wire bonds or conductive epoxy (i.e. components like diode and transistors are fabricated via diffusion as isolated semiconductor. Then they are permanently connected with substrate on suitable spots through extremely thin wires). The wires which bond or inter- connect different components are also made from metal strips on substrate’s surface. In figure 8.15, a peculiar thin film Integrated Circuitsstructure has been displayed.
Figure 8.15 A thin-film IC structure
Substrate, on which a thin filmed / layer circuit is fabricated, is usually smaller than I square inch in size. A thick nichrome or tantalum film is deposited above substrate fabrication of a resistor (the thickness of film normally is even less than 0.0001”). The value of resistor depends on length, breadth and thickness of nicrome or tantalum film manufactured on the surface of substrate. The value of a wide kind of a resistor is low whereas value of a lengthy and thin type of resistor is high. The conductors, which interconnect these resistors, are made from extremely thin film-made metal strips, which are built on the substrates’ surface. For this purpose, metals usually with low resistance are used (e.g. aluminum, gold, platinum etc.). Through thin film technique, it is possible to fabricate resistors of an extremely accurate value and values ranging from few ohms to 100 ohms.
Thin filmed capacitors contain two thin metal films, within which another die-electric film does exist. One metal layer is constructed on substrate, after which another oxide (tantalum oxide, silicon oxide or aluminum oxide) film is deposited above this layer, which functions as a die-electric. A gold or platinum film is deposited over die-electric which functions as an upper capacitors’ plate. The value of capacitances can be changed via variations in plate area, changing thickness of die-electric or by changes in material used as die-electric.
The following two methods are used for the fabrication of thin films.
In this method, a substrate manufactured from a glass or ceramic, is placed in a vacuum, on which vaporized material is then deposited. In other words, material which is used for construction of thin film components and conductors is deposited or collected over substrate through the process of evaporation, until entire material turns into vapors. These vapors deposit on substrate in the shape of thin film/layer after getting cool.
Thick Film Integrated Circuits
Thick-film ICs are manufactured somewhat differently compared to thin–film ICs. In thick film ICs, capacitors, resistors and conductors are fabricated/ printed on a ceramic substrate through silk screen printing techniques. That’s why these circuits are also sometimes called printed thin film circuits (i.e. in thick film technique, resistors and interconnections are printed on a ceramic substrate). In the silk screen technique, an extremely thin wired screen (fabricated from top-quality stainless-steel mesh) is placed above the substrate and a metal which is ink type, passed through the screen. On the mesh screen, space exists only on some specific spots wherefrom ink is passed and then deposited on a particular substrate spots, whereas holes left on the screen are closed through a specific type of emulsion. Thus, a series of contact wires connecting different components manufactured on substrate is formed. After this printing process, fabricated series (circuit) is heated on an extremely high temperature (above 600˚C) in a furnace. Thus, this painted series becomes hard and forms into low resistance conductors. Remember that just like a thin film Integrated Circuits, active elements (transistors, diodes) in the thick film IC are also externally included as discrete components (i.e. active elements are fabricated separately and then linked with substrate. Thus, the circuit gets completed.
Resistors and capacitors are also fabricated on the substrate surface on the basis of silk screen technique. For this purpose, a suitable material or paste (which is made from metal or organic powder) is printed on a ceramic substrate passing it via a suitable screen. Substrate is then heated up to an extremely high temperature. This process is repeated until the completion of the circuit, by using different kind of paste materials.
After the completion of the silk screen process, the need for some further processing may still be felt e.g. in order to get precise resistor value, it has occasionally to be trimmed slightly. Abrasive technique is used for trimming a resistor, which is also called sand blasting (grinding and finishing of an object via some other scratchy and sharp substance is called abrasion). Thus, such resistors can be manufactured the tolerance power of which is up to 5 per cent and standard value can be between 5-100 ohm. The value of a thick film capacitor is normally low. When urgency for a high value capacitor exists, small sized and high value capacitors are fabricated separately and connected with substrate permanently instead of using thick film capacitors. As the thickness of a thick film (which is normally 0.0001”) formed as a result of silk-screening techniques, is greater compared to a thin film thickness, therefore thick film capacitors are relatively large in size. In figure 8.16, a thick film IC has been displayed in a zoomed /magnified condition.
Figure 8.16 – enlarged portion of thick-film IC
Hybrid or Multichip Integrated Circuits
As the name implies, such type of ICs is manufactured through inter-connecting several discrete chips or via a combination of film and monolithic techniques. In figure, 8.17 structure of a multi-chip integrated circuit has been shown. In such type of Integrated Circuits first active components (diodes and transistors) are fabricated inside silicon wafer through monolithic technique, which is subsequently closed through depositing an insulating layer e.g. silicon dioxide (SiO2). After this, film technique is used for the fabrication of passive components (resistor, capacitors) on SiO2 surface.
Figure 8.17, 8.18 – Hybrid or multi-chip IC
A part of hybrid Integrated Circuits has been illustrated in figure 8.18. All components on the circuit have been fixed on an insulating substrate. A thick film resistor and a discrete capacitor have also been set along a monolithic Integrated Circuits on the substrate. All these components are inter-connected by means of a conductor constructed on substrate through film technique. Monolithic Integrated Circuits has been connected with conductor through thin wires, which are firmly planted on their places. Notches are usually formed on thick film resistor (as shown in the figure). Due to these cuts (notches), the process of abrasion takes place, which is meant to adjust its value. Capacitors used in these circuits are fabricated via the film technique or discretely made capacitors are used (as illustrated vide figure). Conductor has been given the shape of a large round terminal bringing it to the edges of the substrate. When packing of a hybrid circuit is done, appropriate pin soldering is carried out along terminals so that circuit could be used in a proper socket.
As hybrid integrated circuits are manufactured bt using the monolithic, thin and thick film techniques simultaneously and in different styles, thus extremely complicated circuits can be fabricated on the ICs under this technique. Through combined application of monolithic and film techniques, components of extreme accuracy and tolerance can be manufactured. Apart from this, discreetly manufactured components e.g. diodes, transistors and capacitors can also be applied in this technique, because these components are capable of tolerating power in large quantity. Besides, hybrid circuits entail some advantages which are non-existent on a monolithic circuit e.g. despite perfect performance, excellent isolation, fabrication of hybrid circuits in small numbers, it is less costly. Besides, another advantage that hybrid ICs have over monolithic ICs is that capacitors and resistors of maximum possible values can be constructed on it as its circuit design is quite elastic (i.e. circuit design can be changed quite easily). As monolithic circuit and film circuits are jointly used along with discretely constructed components on a hybrid IC, therefore they are heavier at times compared to monolithic ICs. Besides, it is less reliable compared to a monolithic circuit due to the usage of discretely manufactured components. Most of the cost in hybrid fabrication occurs on connecting wires, inter-connections of components in a proper series and their final packing. Therefore, hybrid circuits are designed and packed for certain particular applications. However, if more circuits are required, then monolithic devices are considered better.
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