Several methods for manufacturing high-power LED chips

In order to obtain high-power LED devices, it is necessary to prepare suitable high-power LED chips. The common methods for manufacturing high-power LED chips internationally are as follows:

① Increasing the size. By increasing the effective light-emitting area and size of the single LED, the current flowing through the TCL layer is evenly distributed to achieve the expected luminous flux. However, simply increasing the light-emitting area cannot solve the heat dissipation and light output problems, and cannot achieve the expected luminous flux and actual application effect.

② Silicon backplane flip-chip method. First, prepare a large-size LED chip suitable for eutectic welding, and at the same time prepare a silicon backplane of corresponding size, and make a gold conductive layer and a lead conductive layer (ultrasonic gold wire ball solder joint) for eutectic welding on the silicon backplane, and then use eutectic welding equipment to weld the large-size LED chip and the silicon backplane together. This structure is more reasonable, taking into account both the light output problem and the heat dissipation problem. This is the current mainstream production method of high-power LEDs.

In 2001, Lumileds, an American company, developed an AlGaInN power flip chip (FCLED) structure. Its manufacturing process is as follows: first, a NiAu layer with a thickness greater than 500A is deposited on the P-type GaN on the top of the epitaxial wafer for ohmic contact and back reflection; then a mask is used to selectively etch away the P-type layer and the multi-quantum well active layer to expose the N-type layer; an N-type ohmic contact layer is formed by deposition and etching. The chip size is 1mm×1mm, the P-type ohmic contact is square, and the N-type ohmic contact is inserted in a comb shape, which can shorten the current expansion distance and minimize the expansion resistance; then the AlGaInN chip with metallized bumps is flip-chip soldered on a silicon carrier with an anti-static protection diode (ESD).

③ Ceramic base flip-chip method. First, use LED chip general equipment to prepare LED chips with large light-emitting areas suitable for eutectic welding electrode structures and corresponding ceramic bases, and make eutectic welding conductive layers and lead-out conductive layers on the ceramic bases, and then use eutectic welding equipment to weld large-size LED chips and ceramic bases together. This structure takes into account both light emission and heat dissipation issues, and the ceramic base used is a high thermal conductivity ceramic plate, which has an ideal heat dissipation effect and a relatively low price. Therefore, it is a more suitable base material at present, and can reserve space for future integrated circuit integrated packaging.

④ Sapphire substrate transition method: After growing a PN junction on a sapphire substrate according to the traditional InGaN chip manufacturing method, the sapphire substrate is cut off and then connected with traditional quaternary materials to manufacture a large-size blue light LED chip with upper and lower electrode structures.

⑤AlGaInN silicon carbide (SiC) back-lighting method. Cree, an American company, is the only manufacturer in the world that uses SiC substrate to manufacture AlGaInN ultra-high brightness LEDs. In recent years, the structure of its AlGaInN/SiCa chips has been continuously improved, and the brightness has been continuously improved. Since the P-type and N-type electrodes are located at the bottom and top of the chip respectively, single wire bonding is used, which has good compatibility and is easy to use, thus becoming another mainstream product in the development of AlGaInN LEDs.