1. What is the manufacturing flow of the LED chip?

LED chip manufacturing is mainly for the manufacture of effective and reliable low ohm contact electrode, and can meet the contact material minimum pressure drop and provide welding line pad, as much as possible out of light. Vacuum deposition is usually used in the process of transfer coating, mainly at 1.33 * 10 4Pa in high vacuum, the material is melted by means of resistance heating or electron beam bombardment heating, and at low pressure becomes metal vapor deposited on the surface of the semiconductor material. Generally used P type contact metal, including AuBe, AuZn and other alloys, N surface contact metal often use AuGeNi alloy. The alloy layer formed after coating also needs to be exposed as much as possible through the photolithography process, so that the alloy layer left can meet the requirements of the effective and reliable low ohm contact electrode and welding line pressure pad. After the lithography process is finished, the alloying process is carried out, and alloying is usually carried out under the protection of H2 or N2. The time and temperature of alloying are usually determined by factors such as the properties of the semiconductor material and the type of alloy furnace. Of course, if the blue, green and other chip electrode process is more complex, the need to increase passivation film growth, plasma etching process.

2.LED chip manufacturing process, which processes have a significant impact on their photoelectric properties?

In general, after completion of the main electrical properties of LED epitaxial production has her shape, not producing nuclear chip manufacturing Chang nature change, but not appropriate in coating and alloying process conditions will cause some bad electrical parameters. For example, low or high alloying temperature will cause poor ohmic contact, and poor ohmic contact is the main reason for the high VF in the chip manufacturing. After cutting, if the edge of the chip to some corrosion process, to improve the reverse leakage of the chip will be better help. This is because the diamond edge of the diamond blade cutting, chip edge will remain more crumbs powder, these if stuck in the LED chip PN junction will cause leakage, or even breakdown. In addition, if the surface of the chip lithography stripping is not clean, will cause positive and difficult to weld welding line etc.. If it is the back, it will cause high pressure drop. By surface roughening, into inverted trapezoid structure and other measures in the manufacturing process can improve the light intensity.

3. why should LED chips be divided into different sizes? What is the effect of size on the photoelectric performance of LED?

LED chip size can be divided into small power chip, medium power chip and high power chip according to power. According to customer requirements can be divided into single tube level, digital, dot matrix and decorative lighting categories. As for the specific size of the chip, according to the actual production level of different chip manufacturers, there is no specific requirements. As long as the process pass, can improve the chip unit output and reduce the cost, and will not fundamentally change the photoelectric properties. The current of the chip is in fact related to the current density through the chip. The chip is small, the current is small, the chip is large, and the current is large, and their unit current density is almost the same. If the current usage of the 10mil chip is 20mA, then the 40mil chip can theoretically use 16 times the current, or 320mA. But considering that heat dissipation is the major problem of high current, it has less luminous efficiency than small current. On the other hand, as the area increases, the body resistance of the chip will decrease, so the forward turn-on voltage will decrease.

4. LED power chips generally refers to the large area of the chip? Why?

LED high-power chips for white light can be seen on the market in general around 40mil, the so-called high-power chip power use is generally refers to the power of more than 1W. Since quantum efficiency is generally less than 20%, most of the electrical energy will be converted into heat energy, so the heat dissipation of high-power chips is very important, requiring a larger area of the chip.

5. What are the different requirements of the chip technology and processing equipment for making GaN epitaxial materials in comparison with GaP, GaAs and InGaAlP? Why?

The red and yellow substrate LED chip and four chip common bright red yellow are based on GaP and GaAs compound semiconductor material can generally be made of N type substrate. Photolithography was performed by wet process, and finally, the diamond wheel blade was used to chip. GaN blue chip is used as the sapphire substrate, the sapphire substrate is insulated, so can not be used as a LED, must through the process of dry etching on the epitaxial surface while making P/N two electrodes and through some passivation process. Because the sapphire is very hard, it is difficult to use emery wheel blade into chip. Its process is generally more complex than GaP and LED of GaAs material.

6. What are the structures and characteristics of the transparent electrode chip?

The so-called transparent electrode is to be able to conduct electricity, and the two is to be able to light transmission. This material is now the most widely used in liquid crystal manufacturing process, its name is indium tin oxide, English abbreviation ITO, but it can not be used as a pad. When making, it is necessary to do an ohmic electrode on the surface of the chip, then cover a layer of ITO on the surface and then solder a pad on the surface of the ITO. This leads down from the current distribution to each ohmic contact electrode on the ITO layer, and ITO in the air due to refractive index and refractive index between the epitaxial material, can improve the angle of light, also can increase the luminous flux.

7. What are the main trends in the development of chip technology for semiconductor lighting?

With the development of semiconductor LED technology, its application in lighting field is more and more. Especially, the appearance of white LED is becoming the focus of semiconductor lighting. However, the key chip and packaging technology needs to be improved, and the chips should be high power and high