Optical Semiconductor Manufacturing Process

How are optical semiconductors produced?

Wafers to be processed

Thin films of compound semiconductors are deposited or epitaxially grown on a substrate made of semiconductor materials or insulator like GaAs, InP, GaP, Sapphire, or SiC, and optical and functional 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.

Wafers to be processed

Front-end, back-end, and inspection processes

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. In the testing process to monitor each stage of serial processes, sampling or total inspection is conducted in accordance with procedures to administrate and control the processes and quality for a ultimate guarantee of quality.

Front-end, back-end, and inspection processes

Front-end process

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

Design of element function and related pattern
Film deposition

Film deposition

Process to grow a insulating film, such as oxide or nitride, onto the wafer.

Photolithography

Photolithography

Processes composed of coating photo-resist onto a whole wafer, transferring a pattern from a photo mask, exposure, development, and so on.

Etching

Etching

Chemical or physical microfabrication process to selectively remove parts of a insulating thin film or the bulk of a semiconductor material after UV light illumination onto the photo resist -coated wafer.

Impurity diffusion

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 transfer to make photomask

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.

Wafer Inspection

Back-end process

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 mounting

Wafer dicing

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

Wafer dicing

Die bonding

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

Die bonding

Wire bonding

Make interconnections between a die and the exterior of the package or substrate. The wire is attached at both sides 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.”

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.

Manufacturing process of KYOTO SEMICONDUCTOR Co., Ltd.

Eniwa Plant

Eniwa Plant

Kamisunagawa Plant

Kamisunagawa Plant

KYOTO SEMICONDUCTOR Co., Ltd. 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.