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How to Manufacture DFB Laser Diode Chips & EML Chips

2021-10-26

Today semiconductor chips are more and more widely used in the range from smart phones to computers, from medical equipment to cars. These smaller-than-your-fingernail microchips are some of the most complex devices ever manufactured, which involves hundreds of steps, taking up to 4 months. All the steps must be done in clean room environment, where extensive precautions are taken to prevent contamination by dust and other foreign substances. Let's walk through its production process and get a rough idea of how semiconductor laser chips are made.

 

1. Wafer
The simple element silicon in sand is the starting point for making the microchips that power everything today. Wafers are made of silicon, which is refined and purified from silica sand. The silicon is purified (up to 99.99999999%), molten into silicon ingot, and sliced into wafers.

 

The thinner the wafer (could be as thin as 0.5 mm), the lower the unit cost of production, but also the more demanding for process technology. As for diameter, there are mainly 6-inch, 8-inch and 12-inch. The bigger the size, the more demanding for process technology, but of course, you get more chips from bigger size of wafer.

 

2. Coating
A photoresist film is coated on the surface of the wafer, which can improve the oxidation resistance and temperature resistance of the wafer.

 

3. Photolithography and Etching
The process uses chemicals that are sensitive to ultraviolet light. The shape of the chip can be obtained by controlling the position of the shader. A silicon wafer is coated with a photoresist so that it dissolves in ultraviolet light. This is where the first shade can be used so that the UV direct part is dissolved, which can then be washed away with a solvent. The shape of the rest is the same as the shading, which is exactly what we want as schematics. And that gives us the silicon dioxide layer that we need.

 

At the end of the photoetching process, engineers add ions to the wafer and create transistors by injecting impurities into the silicon structure to control electrical conductivity and a chain of physical processes. After the transistors, diodes and other electronic components on the wafer are made, copper is poured into a groove to form precise wiring that connects many of the transistors together. Microchips are made by building up to 100 layers of interconnected patterns on a silicon wafer.

 

4. Wafer Test
After the above processes, a lot of lattice grains (dies) will be formed on the wafer. The correct performance of each die were tested - a process performed by a piece of test equipment called a wafer prober. Wafer test is such an extremely complicated process, and there are generally a large number of dies on the wafer, so it requires the mass production of chips of the same specifications to lower the relative cost.

 

5. Encapsulation
Dies on the wafer are diced from each other, and good ones are fixed, bound to pins, and then placed into various supporting forms that enable them to be plugged into circuit boards. Now we have a chip. There are many forms of encapsulation, such as DIP, QFP, PLCC, QFN, etc., which are determined by peripheral factors like customers’ demands, application environment, and so on. This is why the same chip core may have different encapsulation forms.

 

6. Final Test and Packaging
After the above steps, the chip has been completed, and this step is for final testing, removing defective products, and packaging.

 

GLSUN specializes in R&D, production, and sales of high-end semiconductor laser chips. We own and operate a 3,000 square meter III-V Fab, with full range of capabilities from chip design, epitaxy, and wafer processing to testing. Our products include 2.5Gbs, 10Gbs, 25Gbs to 40Gbs DFB laser chips and EML chips.

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