Epitaxial wafers production process is very complex , exhibition
finished wafer , then just nine per wafer at random for testing , meet
the requirements of that yield , the other for defective products (
voltage deviation is large, the wavelength is shorter or partial long ) .
An epitaxial wafer yield must begin electrode (P pole , N pole ) , the
next to the wafer by laser cutting , sorting and hundred percent ,
depending on the voltage , wavelength, brightness fully automated
sorting , which is formed LED street lighting
chip ( side pieces ) . Then have to be visually inspected , put a
little defective or the electrodes are worn , sorting out , these are
behind the bulk crystal . At this point in the blue membrane of normal
shipments do not meet the requirements of the wafer , it naturally
became the side pieces or raw footage and so on. Defective products
epitaxial wafers ( mainly some parameters do not meet the requirements )
, they do not do the film, directly as electrode (P pole , N pole ) ,
nor do sorting , that is currently on the market LED circle piece (
there is also a good thing, such as square tablets , etc. ) .
Semiconductor manufacturers are mainly polished Si wafer (PW) and the
epitaxial Si film as an IC raw materials. Began in the early 1980s with
the epitaxial film , which has the standard PW do not have some of the
electrical characteristics and eliminates many of the crystal growth and
the subsequent processing of the wafer surface into / near-surface
defects.
Historically , the wafer is a Si wafer manufacturers and personal use, the amount is not in an IC , it needs to be deposited on the surface of single-crystal Si wafer, a thin single-crystal Si layer . The epitaxial layer has a thickness generally 2 ~ 20μm, and the Si substrate having a thickness of 610μm (150mm diameter plate and 725μm (200mm film ) .
Epitaxial deposition can ( also ) a processing multi-chip , also can be processed monolithic . Monolithic reactor can produce the best quality of the epitaxial layer ( thickness , resistivity uniformity, fewer defects ) ; This epitaxial wafers for 150mm ” cutting edge ” products and all major 200mm production .
Extension products
Extension products used in four aspects , CMOS Complementary Metal Oxide Semiconductor requiring small size of the device supports the forefront of technology . CMOS wafer product is the largest application area for the IC manufacturer and is unrecoverable device technology , including a microprocessor and logic chips and memory, flash memory , and application of a DRAM (Dynamic Random Access Memory ) . Requirements for the manufacture of discrete semiconductors Si characteristics with precision components. “Strange ” (exotic) semiconductor class contains some special products, they use non- Si materials , many of which use the compound semiconductor material into the epitaxial layer. Buried layer within a semiconductor device using bipolar transistors physical isolation heavily doped region , which is deposited in the epitaxial process .
Currently , 200mm wafers , epitaxial wafers accounted 1/3.2000 years, including buried layer including , for CMOS logic devices of all epitaxial wafers 69%, DRAM 11% , discrete devices accounted for 20 % to 2005 , CMOS logic will account for 55%, DRAM accounted for 30% , 15% discrete devices .
LED epitaxial wafers – the substrate material
Substrate material is a semiconductor lighting industrial technology cornerstone of the development . Different substrate materials require different epitaxial growth technology, chip processing technology and device packaging technology, substrate material determines the semiconductor lighting technology roadmap . The choice of substrate material depends on the following nine areas:
1, the structure characteristics, the epitaxial crystal structure of the substrate material with the same or similar lattice constant mismatch is small , good crystallinity , defect density
2 , the interface characteristics, and is conducive to the nucleation and epitaxial material adhesion strength
3 , good chemical stability , the epitaxial growth temperature and the atmosphere are not easily decomposed and corrosion
4 , good thermal properties , including thermal conductivity and thermal mismatch is small
5 , good conductivity , can be made down the structure
6 , the optical properties, the production of the device emitted light absorbed by the substrate Small
7 , good mechanical properties , easy processing devices , including thinning , polishing and cutting , etc.
8 , low prices
9 , large size, generally requires not less than 2 inches in diameter .
While the substrate is selected to satisfy the above nine areas is very difficult . Therefore, the current technology can only be changed by epitaxial growth and device processing adjustments to accommodate different substrate semiconductor light emitting device development and production. GaN substrate material for more research , but can be used for the production of substrates currently only three, namely, Al2O3 and sapphire and silicon carbide SiC substrate Si substrate .
Evaluation of the substrate material must be integrated into the following factors:
1 substrate and the epitaxial film structure matches : epitaxial materials and substrate materials identical or similar crystal structure , lattice constant mismatch is small, good crystallinity , low defect density ;
(2) the substrate and the epitaxial film matching the thermal expansion coefficient : Thermal expansion coefficient matching is important , the epitaxial film and the substrate material on the difference in the thermal expansion coefficient is too large may not only decrease the quality of the epitaxial film , but also during operation of the device , since the heat and cause damage to the device ;
3 substrate and the chemical stability of the epitaxial film matching : a substrate material have good chemical stability, the epitaxial growth temperature and the atmosphere are not easily decomposed and corrosion , not because of a chemical reaction with the epitaxial film decline in the quality of the epitaxial film ;
4 Materials degree of difficulty and the level of costs : Taking into account the needs of industrial development , the preparation of the substrate material requirements of simple, cost should not be very high. Size of the substrate is generally not less than 2 inches.
Currently used for GaN-based LED substrate material more, but can be used for the commercialization of substrate present, only three, namely sapphire and silicon carbide and silicon substrate . Others, such as GaN, ZnO substrate is still in the development stage, is still some distance away from the industry .
GaN :
Ideal for the growth of GaN single crystal substrate is a GaN material , can greatly improve the crystal quality of the epitaxial film , reducing the dislocation density and improve the life of the device , improve the luminous efficiency and current density of the device . But the fabrication of GaN single crystal is very difficult, so far there has not been an effective approach.
Zinc oxide:
ZnO has become a candidate for GaN epitaxial substrate , because both have very striking similarities. Both the same crystalline structure , lattice degree of recognition is very small , close to the band gap ( energy band discontinuity value is small, the contact barrier smaller). However , ZnO as the Achilles heel of GaN epitaxial substrate in GaN epitaxial growth temperature and atmosphere of decomposition and corrosion. Currently , ZnO semiconductor materials used to manufacture optoelectronic devices still can not or high temperature electronic devices, the device is not up to the level of quality of materials and the P -type doping problem is not a real solution , suitable for the growth of ZnO-based semiconductor material device has not yet developed.
Sapphire :
The most commonly used for GaN growth substrate is Al2O3. Its advantages are good chemical stability, does not absorb visible light , affordable , manufacturing technology is relatively mature . Although the poor thermal conductivity of the device is not exposed to a small current work is obviously inadequate, but in power type devices working under high current problem is very prominent.
SiC :
SiC as a substrate material after the extent of the application of sapphire, China’s current LatticePower of Professor Jiang Fengyi grown on Si substrates that can be used for commercial LED street lighting epitaxial wafers . Si substrate in thermal conductivity , stability is superior to sapphire , the price is much lower than the sapphire , is a very promising substrates . SiC substrate has good chemical stability, good electrical conductivity , good thermal conductivity , does not absorb visible light , but also very less prominent, such as the price is too high, the crystal quality Al2O3 and Si so difficult to achieve good machining performance is relatively poor, in addition , SiC substrate below 380 nm ultraviolet absorption , not suitable for development of UV below 380 nm LED. useful as the conductivity of the SiC substrate and the thermal conductivity, the power can solve the problem of heat dissipation device type GaNLED , therefore, in the field of semiconductor lighting technology occupies an important position .
Compared with sapphire , SiC and GaN epitaxial film is improved lattice match . Moreover , SiC has a blue light emitting properties, and low resistivity material , can produce an electrode , the device prior to the epitaxial film in the packaging fully tested possible increase of SiC as a substrate material competitiveness. As a layered structure of SiC easy cleavage of the substrate and the epitaxial film of high quality can be obtained between the cleavage planes , which will greatly simplify the structure of the device ; , but also due to its layered structure to the substrate surface often epitaxial film step introduction of a large defect appears.
To achieve the goal of hope luminous efficiency GaN substrate of the LED, low-cost, but also through the GaN substrate lead to efficient, large-area , single lamp power to achieve, as well as technology -driven simplification and yield significantly increased. Semiconductor lighting once become a reality, as significant as Edison invented the incandescent lamp . Once the substrate achieve breakthroughs in key technologies , and its industrialization process will achieve rapid development.
Source from:http://www.lighting-ledlight.com/
Historically , the wafer is a Si wafer manufacturers and personal use, the amount is not in an IC , it needs to be deposited on the surface of single-crystal Si wafer, a thin single-crystal Si layer . The epitaxial layer has a thickness generally 2 ~ 20μm, and the Si substrate having a thickness of 610μm (150mm diameter plate and 725μm (200mm film ) .
Epitaxial deposition can ( also ) a processing multi-chip , also can be processed monolithic . Monolithic reactor can produce the best quality of the epitaxial layer ( thickness , resistivity uniformity, fewer defects ) ; This epitaxial wafers for 150mm ” cutting edge ” products and all major 200mm production .
Extension products
Extension products used in four aspects , CMOS Complementary Metal Oxide Semiconductor requiring small size of the device supports the forefront of technology . CMOS wafer product is the largest application area for the IC manufacturer and is unrecoverable device technology , including a microprocessor and logic chips and memory, flash memory , and application of a DRAM (Dynamic Random Access Memory ) . Requirements for the manufacture of discrete semiconductors Si characteristics with precision components. “Strange ” (exotic) semiconductor class contains some special products, they use non- Si materials , many of which use the compound semiconductor material into the epitaxial layer. Buried layer within a semiconductor device using bipolar transistors physical isolation heavily doped region , which is deposited in the epitaxial process .
Currently , 200mm wafers , epitaxial wafers accounted 1/3.2000 years, including buried layer including , for CMOS logic devices of all epitaxial wafers 69%, DRAM 11% , discrete devices accounted for 20 % to 2005 , CMOS logic will account for 55%, DRAM accounted for 30% , 15% discrete devices .
LED epitaxial wafers – the substrate material
Substrate material is a semiconductor lighting industrial technology cornerstone of the development . Different substrate materials require different epitaxial growth technology, chip processing technology and device packaging technology, substrate material determines the semiconductor lighting technology roadmap . The choice of substrate material depends on the following nine areas:
1, the structure characteristics, the epitaxial crystal structure of the substrate material with the same or similar lattice constant mismatch is small , good crystallinity , defect density
2 , the interface characteristics, and is conducive to the nucleation and epitaxial material adhesion strength
3 , good chemical stability , the epitaxial growth temperature and the atmosphere are not easily decomposed and corrosion
4 , good thermal properties , including thermal conductivity and thermal mismatch is small
5 , good conductivity , can be made down the structure
6 , the optical properties, the production of the device emitted light absorbed by the substrate Small
7 , good mechanical properties , easy processing devices , including thinning , polishing and cutting , etc.
8 , low prices
9 , large size, generally requires not less than 2 inches in diameter .
While the substrate is selected to satisfy the above nine areas is very difficult . Therefore, the current technology can only be changed by epitaxial growth and device processing adjustments to accommodate different substrate semiconductor light emitting device development and production. GaN substrate material for more research , but can be used for the production of substrates currently only three, namely, Al2O3 and sapphire and silicon carbide SiC substrate Si substrate .
Evaluation of the substrate material must be integrated into the following factors:
1 substrate and the epitaxial film structure matches : epitaxial materials and substrate materials identical or similar crystal structure , lattice constant mismatch is small, good crystallinity , low defect density ;
(2) the substrate and the epitaxial film matching the thermal expansion coefficient : Thermal expansion coefficient matching is important , the epitaxial film and the substrate material on the difference in the thermal expansion coefficient is too large may not only decrease the quality of the epitaxial film , but also during operation of the device , since the heat and cause damage to the device ;
3 substrate and the chemical stability of the epitaxial film matching : a substrate material have good chemical stability, the epitaxial growth temperature and the atmosphere are not easily decomposed and corrosion , not because of a chemical reaction with the epitaxial film decline in the quality of the epitaxial film ;
4 Materials degree of difficulty and the level of costs : Taking into account the needs of industrial development , the preparation of the substrate material requirements of simple, cost should not be very high. Size of the substrate is generally not less than 2 inches.
Currently used for GaN-based LED substrate material more, but can be used for the commercialization of substrate present, only three, namely sapphire and silicon carbide and silicon substrate . Others, such as GaN, ZnO substrate is still in the development stage, is still some distance away from the industry .
GaN :
Ideal for the growth of GaN single crystal substrate is a GaN material , can greatly improve the crystal quality of the epitaxial film , reducing the dislocation density and improve the life of the device , improve the luminous efficiency and current density of the device . But the fabrication of GaN single crystal is very difficult, so far there has not been an effective approach.
Zinc oxide:
ZnO has become a candidate for GaN epitaxial substrate , because both have very striking similarities. Both the same crystalline structure , lattice degree of recognition is very small , close to the band gap ( energy band discontinuity value is small, the contact barrier smaller). However , ZnO as the Achilles heel of GaN epitaxial substrate in GaN epitaxial growth temperature and atmosphere of decomposition and corrosion. Currently , ZnO semiconductor materials used to manufacture optoelectronic devices still can not or high temperature electronic devices, the device is not up to the level of quality of materials and the P -type doping problem is not a real solution , suitable for the growth of ZnO-based semiconductor material device has not yet developed.
Sapphire :
The most commonly used for GaN growth substrate is Al2O3. Its advantages are good chemical stability, does not absorb visible light , affordable , manufacturing technology is relatively mature . Although the poor thermal conductivity of the device is not exposed to a small current work is obviously inadequate, but in power type devices working under high current problem is very prominent.
SiC :
SiC as a substrate material after the extent of the application of sapphire, China’s current LatticePower of Professor Jiang Fengyi grown on Si substrates that can be used for commercial LED street lighting epitaxial wafers . Si substrate in thermal conductivity , stability is superior to sapphire , the price is much lower than the sapphire , is a very promising substrates . SiC substrate has good chemical stability, good electrical conductivity , good thermal conductivity , does not absorb visible light , but also very less prominent, such as the price is too high, the crystal quality Al2O3 and Si so difficult to achieve good machining performance is relatively poor, in addition , SiC substrate below 380 nm ultraviolet absorption , not suitable for development of UV below 380 nm LED. useful as the conductivity of the SiC substrate and the thermal conductivity, the power can solve the problem of heat dissipation device type GaNLED , therefore, in the field of semiconductor lighting technology occupies an important position .
Compared with sapphire , SiC and GaN epitaxial film is improved lattice match . Moreover , SiC has a blue light emitting properties, and low resistivity material , can produce an electrode , the device prior to the epitaxial film in the packaging fully tested possible increase of SiC as a substrate material competitiveness. As a layered structure of SiC easy cleavage of the substrate and the epitaxial film of high quality can be obtained between the cleavage planes , which will greatly simplify the structure of the device ; , but also due to its layered structure to the substrate surface often epitaxial film step introduction of a large defect appears.
To achieve the goal of hope luminous efficiency GaN substrate of the LED, low-cost, but also through the GaN substrate lead to efficient, large-area , single lamp power to achieve, as well as technology -driven simplification and yield significantly increased. Semiconductor lighting once become a reality, as significant as Edison invented the incandescent lamp . Once the substrate achieve breakthroughs in key technologies , and its industrialization process will achieve rapid development.
Source from:http://www.lighting-ledlight.com/
No comments:
Post a Comment