The front-end process refers to the formation of the light-emitting and photo-detecting elements directly on the silicon or compound semiconductor wafer and provides a process flow in the procedure below.

Design of element function and related pattern
Design the functions and structures of some elements, according to customer demands.

Design and fabrication of photo-masks
Design and fabricate a photo-mask to transfer thousands of patterns of some element onto a glass plate.

Pattern formation
Create thousands of elements on a wafer. through the processes below.

• Film deposition (Process to grow a insulating film, such as oxide or nitride, onto the wafer.)
• Photolithography (Processes composed of coating photo-resist onto a whole wafer, transferring a pattern from a photo mask, exposure, development, and so on.)
• Etching (Chemical or physical microfabrication process to selectively remove parts of a insulating thin film or the bulk of a semiconductor material after exposure to UV light.)
• Impurity diffusion (Process to diffuse some dopant of p or n type into the very high-purity semiconductor wafers and modify electrical properties, forming P/N junction on the surface.)

The abovementioned steps are repeated to fabricate elements according to the process flow chart.

Electrode formation
Make ohmic contacts with the p or n region, and, in an optical semiconductor element having polarity, the anode is the positive (+) electrode and the cathode is the negative (-) electrode.

Wafer Inspection
Electrical performance is proved on a test machine, so-called a prover. This process is also known as wafer proving or wafer sorting test. All of individual elements connected on a wafer are subjected to such an electrical test for functional imperfections and are determined as good with meeting the requested specifications.

(1)Photomask alignment

(2)Thin film deposition

(3)Impurity diffusion

The back-end process consists of 4 steps: wafer mounting, die bonding, wire bonding, and packaging.

Wafer mounting
Mount a whole wafer onto an adhesive tape and attach it onto a ring before breaking it into individual pieces.

Wafer dicing
Cut a wafer containing thousands of elements into individual pieces, each called a die.

Die bonding
Mount or fix a die into the package or some substrate; also called die attachment.

Wire bonding
Make interconnections between a die and the exterior. The wire is attached at both ends by using some combination of heat, pressure, and ultrasonic energy to weld each end.

Visual inspection
Check visually die location, epoxy paste, and wiring.

Packaging
Encapsulate a die with plastic resin such as silicone or epoxy to prevent physical damage or chemical corrosion. The term of "encapsulation" is sometimes used synonymously with "packaging."

Finished product inspection
Such optical semiconductor devices are subject to a variety of qualification test for electrical characteristics to verify whether they function properly. The proportion of optical devices found to perform properly is referred to as the yield.

Wafer dicing

Die bonding

Wire bonding

Kyosemi Corporation is a dedicated manufacturer of optical semiconductor devices as above mentioned. The company has established an integrated production line covering successively 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 continuously carried out for mass production at the Eniwa Plant, but some of them are transferred for further cost reduction and mass production to the Kamisunagawa Plant, in Kamisunagawa-cho, Sorachi-gun, Hokkaido, Japan.
Both plants are located at Northern Part of Japan.

Eniwa Plant

Kamisunagawa Plant