LED by the extension of knowledge - (AddTime ：2013-01-03)

Extension of the production process is very complicated, show the extension, the next in each extension of random sampling test at nine o 'clock, conform to the requirements of the product is good, the other for bad product (voltage deviation, short or long wavelength, etc.). Good product extension of electrodes will start to do (P, N), then use laser cutting extension, then hundred separated, according to the different voltage, wavelength, intensity of automatic HuaFen inspection, is formed 200W led Flood light chip (party). And then, a little defective to visual or electrode wear, working out, these are the back of the scattered. At this time on the blue film have not meet the requirements of the normal shipment chips, also is the natural or feather bar, etc. Non-conforming slices of extension (mainly some parameters do not conform to the requirements), don't have to do party, is directly do electrode (P, N), also don't do the sorting, which is on the market at present the 200W led Flood light wafer (there are good things, such as square slice).

Semiconductor manufacturers main use polishing Si Si (PW) and extension tablet as IC of raw materials. Start using extension in the early 1980 s, it has a standard pwi didn't have some of the electrical characteristics and eliminate a lot in the crystal growth and subsequent chip is introduced in the machining surface or near surface defects.

History, extension is composed of Si tablet manufacturers and for personal use and in IC dosage is not big, it need to be on the surface of single crystal Si deposited on a thin layer of single crystal Si. General extension the thickness of the layer of 2 ~ 20 mu m, and the thickness of the substrate Si for 610 mu m (150 mm in diameter and 725 mu m (200 mm).

Extension deposition can (also) a more pieces of processing, also can be processed single piece. Monolithic reactors to produce the best quality extension layer (thickness, good uniformity of the resistivity, less defect); This extension to 150 mm 200 mm "frontier" products and all important products of the production.

Extension products
Extension products applied in four aspects, CMOS complementary metal oxide semiconductor device support for small size of the front process. CMOS product is the extension of the biggest application fields, and is used in IC manufacturers do not recover devices process, including chip microprocessor and logic and memory applications of flash memory and DRAM (dynamic random access memory). Discrete semiconductor used in the manufacture of precision component with the characteristics of Si are required. "Strange" (exotic) semiconductor category contains some special products, they want to use non Si materials, many of them want to use compound semiconductor materials incorporated into extension. Buried layer semiconductor of bipolar transistor devices within the weight doped area of physical isolation, this also is deposited in the extension process. At present, 200 mm chip, extension of accounts for 1/3.2000, including buried layer, logic devices used for the CMOS account for 69% of all the denotation of DRAM (11%), discrete components accounted for 20% by the year 2005, CMOS logic will account for 55%, 30% DRAM, discrete components accounted for 15%. 200W led Flood light extension of - substrate materials
Substrate is the cornerstone of semiconductor lighting industry technology development. Different substrate material, need different extension growth technology, chip processing technology and device packaging technology, substrate material determines the development of semiconductor lighting technology route. The choice of substrate materials mainly depends on the following nine aspects:

1, structural characteristics, extension material with same or similar crystal structure, the lattice constants of the substrate mismatch of small, good crystallization properties and defect density
2, good interfacial characteristics, be helpful for extension materials nucleation and strong adhesion
3, good chemical stability, the extension growth it is not easy to break down the temperature and atmosphere and corrosion
4, good thermal performance, including good thermal conductivity and thermal mismatch of small
5, good conductivity, can be made up and down
6, good optical properties, production from the components of the light absorbed by the substrate
7, good mechanical properties, the device is easy to processing, including thinning, polishing, cutting, etc
8, the price is cheap
9, large size, general requirement not less than 2 inches in diameter.

The choice of substrate to satisfy more than nine aspects is very difficult. So, at present only by extension growth technical modification and adjustment of device processing technology to adapt to different substrate on the research and development and production of the semiconductor light emitting devices. Used for the study of gallium nitride substrate material is more, but at present only three can be used in the production of substrate, the sapphire Al2O3, and SiC SiC substrate and Si substrate. Evaluation of substrate materials must be comprehensive consideration the following factors: 1. The substrate and the structure of the membrane matching: extension the crystalline structure of the material and the substrate material the same or similar, small lattice constant mismatch, crystallization good performance, low defect density;
2. Substrate and extension of the thermal expansion coefficient matching: thermal expansion coefficient of the match is very important, extension film and substrate material on the thermal expansion coefficient vary too big not only could make extension film quality decline, will be in the device work process, caused by heating the damage of the device;
3. Substrate and denotation membrane chemical stability matching: substrate material to have a good chemical stability, the extension of growth temperature and atmosphere is not easy to decompose and corrosion, not because the chemical reaction of extension and denotation membranes quality decline;
4. The discretion of the difficulty and cost of the preparation of materials: considering the needs of the development of industrialization, the preparation of the substrate material requirements is concise, cost is not high. Substrate size is not less than 2 inches. Current used in GaN, 200W led Flood light the substrate material is more, but can be used to the commercialization of substrate is only three, namely sapphire and silicon carbide and silicon substrate. Other such as GaN, ZnO substrate is still in development stage, with the industrialization of a distance away. Gallium nitride:

Is the ideal substrate for the growth of GaN GaN epitaxial material, can greatly improve the quality of extension of the crystals, reduce dislocation density, improve the working life of the device, improve the luminous efficiency, improve the device working current density. But the preparation of GaN body single crystal is very difficult, so far no effective. Zno:

ZnO can be GaN extension of candidate substrate, because is very striking similarities between the two. Both crystal structure, the lattice recognition degree is very small, forbidden band width to (take discrete value is small, the small contact potential barrier). However, ZnO as GaN substrate extension of fatal weakness is in the growth of GaN extension easy decomposition temperature and atmosphere and corrosion. At present, ZnO semiconductor material is not used to making optoelectronic devices or high temperature electronic components, mainly is the material quality can not reach the device level and P type doped problem did not get real solution, suitable for the growth of ZnO and semiconductor materials equipment has not yet been developed.

Blue precious stone:
Used in GaN growth is the most common substrate Al2O3. Its advantage is good chemical stability, not absorb visible light, moderate price, manufacturing technology is relatively mature. Although poor thermal conductivity in the device small current work without exposure, but in power type device big problems under the current work is very outstanding. Silicon carbide.
SiC as substrate material of widely used degree after sapphire, at present China's crystal can grow photoelectric JiangFengYi professor on the Si substrate out can be used for commercial 200W led Flood light extension. Si substrate is superior to the sapphire in thermal conductivity and stability, price is much lower than the sapphire and is a very promising substrate. SiC substrate with good chemical stability, good conductivity, good thermal conductivity, don't absorb visible light, but insufficient also very outstanding, such as the price is too high, crystal quality is difficult to achieve the Al2O3 and Si so well, mechanical processing performance is bad, in addition, SiC substrate absorb below the 380 nm uv light, not suitable for development of less than 380 nm uv 200W led Flood light . Due to the SiC substrate good conductivity and thermal conductivity, can well solve the problem of heat dissipation power type GaN 200W led Flood light device, it occupies an important position in the field of semiconductor lighting technology.

Compared with sapphire, SiC and GaN extension of lattice match improved. In addition, SiC with blue light emitting properties, but also to the low resistance materials, can make electrode, the device extension membrane to complete before packaging test becomes possible, and to enhance the competitiveness of SiC as substrate material. Due to the layer structure of SiC easy to cleavage, between substrate and extension membrane can get high quality of the cleavage plane, this will greatly simplify the structure of the device; But at the same time because its layer structure, on the surface of the substrate is to extension membrane into the steps of a large number of defects. Realize the goal of the luminous efficiency to hope that GaN substrate 200W led Flood light , to realize low cost, also want to through the GaN substrate in high efficiency, large area, the realization of the single lamp power and drive technology of the simplified and greatly improve the yield. Semiconductor lighting once become a reality, its significance as Edison invented incandescent lamp. Once made breakthroughs in key technology such as substrate, the industrialization will get rapid development.