The manufacturing process of semiconductor lasers has many similarities with the process of semiconductor electronic devices in principle. It requires many manufacturing process steps in order to get one semiconductor laser module. Although the structural designs, and the manufacturing processes of various semiconductor lasers are quite different, they have similarities.
Basic process: selection and preparation of substrates, epitaxial growth, corrosion, diffusion, electrode production, cleavage or dicing, rack LD making, aging screening, packaging coupling, overall test.
The choice of substrate is the first step in device manufacturing. It is something used for epitaxial growth. Since the quality of epitaxial growth is obviously affected by the crystalline quality of the substrate, the substrate must be considered to match the lattice of the heterojunction material (sometimes with a buffer layer); it has a prescribed crystal orientation and a certain deviation range; appropriate doping concentration; certain thickness; the density of defects on the surface and inside should be low, and the surface should be smooth and bright without scratches.
The epitaxial growth process is the core process in the manufacture of semiconductor lasers, and it is a key step in determining device performance and yield. Epitaxial growth is the growth of multiple or multiple compounds or alloys (solid solutions) on the substrate to form a homojunction or heterojunction. Commonly used epitaxial growth processes include LPE, MOCVD, MBE, etc.
Corrosion is an important process link to prepare various shapes according to the structure of the laser design and the materials used. It is divided into wet (chemical) etching and dry etching (plasma etching, reactive ion etching, magnetic cyclotron resonance etching, etc.), each with its own application range. Dry etching is mainly used for fine etching of small sizes.
Diffusion is a very mature and increasingly important technology in semiconductor manufacturing. The use of diffusion technology can change the electrical and optical properties of semiconductor materials.
Electrode production is also called ohmic contact, which not only affects the power conversion of the device, but also directly affects the reliability and life of the device.
The cleavage technology is a technology in which the epitaxial chip is cleaved into a single chip after metallization (ohmic contact production), and a parallel reflective cavity surface (ie F-P cavity) is obtained.
Soldering is to sinter the qualified die on the heat sink with solder. There are two welding methods: vacuum welding and forming gas welding, which are mainly selected according to the nature and process of the solder. When soldering, it is necessary to maintain a firm bond and uniform adhesion, but not too much solder and not too high temperature to prevent the solder from overflowing the bottom surface and destroying the cleavage surface, or even contaminating the active area.
Bonding is to connect the electrode to the die by ultrasonic welding or thermal compression welding of the gold wire or gold foil strip, or both, as a lead for current injection.
In order to improve reliability, the packaging should be fully metallized and airtight. In some cases, temperature control, light control sensors, semiconductor coolers, and sometimes drive circuits are also installed in the shell, depending on the specific requirements. Through the above process, a practical semiconductor laser device/module can be obtained.
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