INTRODUCTION
Electronics deals with the circuit or device in which conduction take place with the movement of electrons in vacuum, semiconductor or a gas. Till mid 20th century vacuum tubes were the major part of the electronic devices. Vacuum tubes are the devices which controls the flow of electrons between electrodes in evacuated containers. Vacuum tubes were used in radio, television, phonograph, radar etc. But these tubes were bulky and consumes more power. In the mid 20th century Integrated circuits(IC) were introduced which brought a drastic change in the field of electronics. IC’s consists of small semiconductor devices integrated on a single chip. The evolution of the integrated circuits started with few transistors on the single …show more content…
Gross defects are caused due to scratches from wafer mishandling and also in etching process during fabrication process. These type of defects can cause large area defects and affect the chip largely. But Gross area defects are east to identify and it can be almost eliminated. The frequency of global area defects is independent of the die size and therefore it can be considered as the main reason for large area defects. Second type of faults are Spot defects which are small area defects caused due to undesired chemical, airborne particles deposited on the wafer during fabrication of the chip, this type of faults are difficult to eliminate. Spot defects are proportional to chip area which means spot defects increases by increasing the size of the chip area. So yield loss is higher in Spot defects. Spot defects can be categorized into different types according to their factors like size of the defect, position of the defect, potential to harm the chip, some may cause missing patterns which may result in open circuits and may also cause extra pattern which may result in short circuit. Further spot defects can be classified into intra layer defects and inter layer defects. Intra layer defects are caused due to particles deposited during lithography and also known as photolithographic defects. Examples of intra-layer defects are extra metal, polysilicon and diffusion. Interlayer defects are missing material in the vias between two metals and extra material. Example of interlayer defect is dust particles. Due to different manufacturing and circuit fault the yield of the chip is reduced. It is not possible to get 100% yield of the chip due to the faults, but we can enhance the yield of the chip by using different yield enhancement techniques. Yield enhancement techniques are introduced to improve the yield of the chips by incorporating redundancy to the design and modifying the floor plan and its layout and making chip fault tolerant.