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Wafers to be processed |
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Thin films of compound semiconductors are deposited or epitaxially grown on a substrate made of substances like GaAs, InP, GaP, Sapphire, or SiC, and optical devices are created on these substrates.
The substrate thickness is 0.25-1.0mm with a diameter of 2 to 5 inches (50 to 100mm), and the film is usually grown to a thickness of about 0.05-0.2mm. The substrate shape is usually round and so is called a wafer. |
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Front-end, back-end, and inspection processes |
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| Once the wafers are prepared, a multi-step sequence is carried out to create the desired semiconductor devices. In general, optical semiconductor fabrication is grouped into two processes: the front-end process and the back-end process. In the front-end process, wafers are engineered, and in the back-end process, they are separated into individual elements or chips, and finally all the qualified chips are assembled into packages. To ensure strict quality control, tests, such as sampling or inspection of all chips, are carried out. |
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Front-end process |
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| The front-end process refers to the formation of the light-emitting and photo-detecting devices directly on the silicon or compound semiconductor wafer and follows the procedure below. |
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Device design and pattern design
(Design the functions and structures, according to customer demands.) |
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Design and fabrication of photomasks
(Transfer thousands of patterns of some element onto a glass plate.) |
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Pattern formation
(Create thousands of devices on the wafer.) |
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Film deposition (Process to grow a material, such as oxide or nitride, onto the wafer.) |
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Photolithography (Process to transfer a pattern from a photomask onto the wafer.) |
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Etching (Process to remove material from the wafer in bulk or selective form.) |
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Impurity diffusion (Process to introduce p or n dopants to modify electrical properties.) |
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| The abovementioned steps are repeated according to the process flow chart. |
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Electrode formation
(Make ohmic contacts with the p or n region, and, in an optical semiconductor device having polarity, the anode is the positive (+) electrode and the cathode is the negative (-) electrode.) |
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Wafer Inspection
(Devices are subjected to various electrical tests to verify that they function properly.) |
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| Photomask alignment |
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| Thin film deposition |
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| Impurity diffusion |
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Back-end process |
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| The back-end process consists of 4 steps: wafer mounting, die bonding, wire bonding, and packaging. |
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Wafer mounting
(Mount the wafer onto adhesive tape and attach this onto a ring.) |
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Wafer dicing
(Cut a wafer containing thousands of elements into individual pieces, each called a die.) |
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Die bonding
(Mount or fix a die to the package or support structure; also called die attachment) |
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Wire bonding
(Make interconnections between a chip and the exterior. The wire is attached at both ends using some combination of heat, pressure, and ultrasonic energy to make a weld.) |
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Visual inspection
(Visually check the location of dies, epoxy paste, and wiring.) |
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Packaging
(Encapsulate the die with ceramic, plastic, or epoxy to prevent physical damage or corrosion. The term of "encapsulation" is sometimes used synonymously with "packaging.") |
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Finished product inspection
(Electrical performances is verified.) The proportion of devices found to perform properly is referred to as the yield.) |
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| Wafer dicing |
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| Die bonding |
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| Wire bonding |
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Kyosemi Corporation |
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Kyosemi Corporation is a dedicated manufacturer of optical semiconductor devices. The company has established an integrated production line covering front-end to back-end processes.
Front-end processes are carried out mainly at the Eniwa Plant in Eniwa City, Hokkaido, Japan.
Back-end processes are carried out at the Eniwa Plant and at the Kamisunagawa Plant, in Kamisunagawa-cho, Sorachi-gun, Hokkaido. |
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| Eniwa Plant including Microgravity Utilization Laboratory |
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| Kamisunagawa Plant |
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