Summary of high-power LED chip fabrication methods

In order to obtain high-power LED devices, it is necessary to prepare appropriate high-power LED chips. There are several common methods for manufacturing high-power LED chips internationally:

    ① Enlarged size method. By increasing the effective luminous area and size of a single LED, the current flowing through the TCL layer is evenly distributed to achieve the expected luminous flux. However, simply increasing the luminous area cannot solve the heat dissipation and light emission problems, and cannot achieve the expected luminous flux and practical application effects.

    ② Flip chip method using silicon substrate. Firstly, a large size LED chip suitable for eutectic welding is prepared, while a corresponding size silicon substrate is prepared. On the silicon substrate, a gold conductive layer for eutectic welding and an outgoing conductive layer (ultrasonic gold wire ball solder joint) are produced, and then the large size LED chip is welded together with the silicon substrate using eutectic welding equipment. This structure is relatively reasonable, taking into account both the issue of light emission and the issue of heat dissipation. This is currently the mainstream production method for high-power LEDs.

    In 2001, Lumileds Company of the United States developed an AlGaInN power type flip chip (FCLED) structure. The manufacturing process is as follows: First, NiAu layers with a thickness greater than 500A are deposited on the P-type GaN on the top of the epitaxial wafer for ohmic contact and back reflection; Then, the P type layer and the multi quantum well active layer are selectively etched using a mask to expose the N type layer; After deposition and etching, an N-type ohmic contact layer is formed, with a chip size of 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 spreading distance and minimize the spreading resistance; Then, the metallized bump AlGaInN chip is flip soldered onto a silicon carrier with an antistatic protective diode (ESD).

    ③ Ceramic bottom flip flop method. Firstly, LED chips with large light emitting areas suitable for eutectic welding electrode structures and corresponding ceramic substrates are fabricated using LED wafer general-purpose equipment, and eutectic welding conductive layers and lead-out conductive layers are fabricated on the ceramic substrate. Then, large LED chips are welded together with the ceramic substrate using eutectic welding equipment. This structure not only considers the issue of light emission but also the issue of heat dissipation. The ceramic bottom plate used is a high thermal conductivity ceramic plate, which has excellent heat dissipation effect and relatively low price. Therefore, it is a relatively suitable bottom plate material at present and can reserve space for future integrated circuit packaging.

    ④ Sapphire substrate transition method. According to the traditional InGaN chip manufacturing method, a PN junction is grown on a sapphire substrate, and then the sapphire substrate is cut off and connected to a traditional quad material to produce a large size blue LED chip with an upper and lower electrode structure.

    ⑤ AlGaInN silicon carbide (SiC) back surface photoluminescence method. Cree Corporation of the United States is the only manufacturer in the world that uses SiC substrates to manufacture AlGaInN ultra-high brightness LEDs. Over the past few years, its AlGaInN/SiCa chips have continuously improved in structure and brightness. Due to the fact that P-type and N-type electrodes are located at the bottom and top of the chip respectively, using single lead bonding, which has good compatibility and is convenient to use, they have become another mainstream product in the development of AlGaInNLED.