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IQE's Epitaxial Wafers Complement Supply Chain
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International Quantum Epitaxial, plc (IQE) claims to be the world's leading "pure play" supplier of compound semiconductor epitaxial wafers, used in many of today's high technology components and systems. With current market capitalization of over US$600 million, IQE is the third largest public listed company in Wales, the UK.
Dr Drew Nelson, the group's CEO and president, talks to NEA about the company's technologies and their potential for the Asia-Pacific market.
NEA: What benefits do compound semiconductors offer?
Dr Nelson: For electronic devices, compound semiconductors offer higher speeds and lower power consumption than pure silicon. The hierarchy, in terms of performance, is: Si, SiGe, GaAs, InP, then GaN. For optoelectronic applications, GaAs- and InP-based devices can emit and receive light across the visible and infrared portions of the electromagnetic spectrum. They are essential for lighting and display technology, as well as communications, data storage (CD/DVD), movement detection (passive infrared), and consumer products (eg, remote controls).
NEA:What is epitaxy? How does it differ from traditional silicon processes?
Dr Nelson:In the semiconductor world, epitaxy is the process of depositing very thin layers of semiconductor materials onto the surface of a single crystal substrate. This is done in a way that ensures that the atomic structure in the deposited layers is perfectly aligned with the crystalline axis within the substrate.
Traditional silicon processes simply use the substrate as a mechanical base on which to build components, while an epitaxial layer or structure is effectively an extension of the substrate. This means that the electronic, optical and physical properties of the material close to the surface can be manipulated to perform a range of functions. In this way, the functionality of devices fabricated into the material is said to be embedded.
The epitaxy process is used to modify the material properties to within a few thousandths of a millimeter at the surface of a substrate. As the material is a single crystal, rather than a device simply fastened to the top of a substrate, an electronic charge can travel much more quickly through the material.
Typically, epitaxy is used to deposit alloys or compounds comprising two or more elements. By carefully selecting the composition of the elements, the structure can be made to respond to, or emit light at, specific wavelengths, from short wavelengths (UV) through the visible spectrum, to long wavelength light or infrared.
NEA:What are the main features and benefits of the different technologies used by IQE?
Dr Nelson:The initial substrates are produced using vertical gradient freeze (VGF) and liquid encapsulated (LEC) technologies. Both techniques are similar in principle in that either a seed crystal of indium phosphide (InP) is pulled from a melt of indium and phosphorous, or a gallium arsenide (GaAs) seed is pulled from a melt of gallium and arsenic, under precisely controlled conditions. As the melt is slowly pulled and rotated, it freezes to form a crystalline boule. This boule is sliced into wafers which form the starting material on which epitaxial layers are grown.
Early techniques for producing InP and GaAs included liquid phase epitaxy (LPE) and vapor phase epitaxy (VPE). Vapor phase epitaxy is also referred to as chemical vapor deposition (CVD). Molecular beam epitaxy (MBE) tends to be used for electronic devices requiring very precise layer control.
LPE is an inefficient process suitable only for simple structures of less than six layers. VPE is a process through which various gasses containing the required elements are flowed over the heated substrates.
MOVPE (or MOCVD, OMVPE, OMCVD) is the same as the VPE process but with the addition of metal organics (or organo-metallics). Metal organics are liquids or powders containing gallium, aluminum and indium, which can effectively be converted into gasses within the VPE equipment. The metal-organics part of the process is essential for facilitating the growth of materials such as gallium arsenide (GaAs), indium phosphide (InP) and other combinations. MOVPE is highly efficient at "growing" thicker layers (up to 10mm). Traditionally, MOVPE has been used to produce optoelectronic products.
With the MBE process, a range of sources are heated in an ultra-high vacuum (UHV) chamber. Traditionally, the MBE process has been used to produce electronic devices that need very sharp interfaces between layers as the level of control is much higher. But the process has slightly slower growth rates than is common with the CVD processes.
NEA:Which applications benefit the most from your products?
Dr Nelson:IQE offers a diverse range of materials systems for both electronic and optoelectronic devices. Pure silicon has a theoretical speed limit of around 2GHz. Current wireless applications typically operate at around 1.8GHz, and as we look towards future generations (eg, 3G telephony), we can anticipate the first applications that are likely to both breach the limit and need the lower power consumption offered by compound semiconductors.
As PC systems get faster, they too will breach the 2GHz limit, and compounds -- whether silicon based (SiGe, strained silicon) or GaAs/InP based -- provide the solution.
High-speed electronics encroaches upon many aspects of technology, and compound semiconductors may be found in space applications, medical devices and automotive systems, as well as consumer and communications products.
As for infrared and visible optical devices, these cover a range of applications, from displays to communications devices.
NEA:What makes IQE stand out from other key industry players?
Dr Nelson:With traditional silicon technologies, there are three basic discreet production stages: wafer supply, wafer fabrication and device packaging. The emergence of new technologies involves the introduction of a significant additional stage between wafer supply and wafer fabrication. This additional stage is epitaxy.
UMC, TSMC and Chartered offer downstream fabrication services for silicon chips. IQE offers enhanced materials (epitaxial wafers) as a foundry service.
As an epitaxial wafer foundry, IQE produces the materials that can be processed using the technology offered by wafer fabrication foundries such as UMC, TSMC and Chartered Semiconductor. As such, IQE's product offerings form a complementary stage in the supply chain.
NEA:Does IQE have any plans to establish a plant or business operations in the Asia-Pacific region?
Dr Nelson:IQE is considering joint ventures in the Asia-Pacific region. A plant or joint venture in Singapore or Taiwan would be ideal because of the proximity to the well-established wafer fabrication foundries, which would be potential customers for our advanced epitaxial wafers. The combination of IQE's materials processing expertise with the region's device processing expertise could offer a one-stop-shop for next-generation technology.
by Adeline Ong, Singapore
(August 2002 Issue, Nikkei Electronics Asia)
Dr Drew Nelson, the group's CEO and president, talks to NEA about the company's technologies and their potential for the Asia-Pacific market.
NEA: What benefits do compound semiconductors offer?
Dr Nelson: For electronic devices, compound semiconductors offer higher speeds and lower power consumption than pure silicon. The hierarchy, in terms of performance, is: Si, SiGe, GaAs, InP, then GaN. For optoelectronic applications, GaAs- and InP-based devices can emit and receive light across the visible and infrared portions of the electromagnetic spectrum. They are essential for lighting and display technology, as well as communications, data storage (CD/DVD), movement detection (passive infrared), and consumer products (eg, remote controls).
NEA:What is epitaxy? How does it differ from traditional silicon processes?
Dr Nelson:In the semiconductor world, epitaxy is the process of depositing very thin layers of semiconductor materials onto the surface of a single crystal substrate. This is done in a way that ensures that the atomic structure in the deposited layers is perfectly aligned with the crystalline axis within the substrate.
Traditional silicon processes simply use the substrate as a mechanical base on which to build components, while an epitaxial layer or structure is effectively an extension of the substrate. This means that the electronic, optical and physical properties of the material close to the surface can be manipulated to perform a range of functions. In this way, the functionality of devices fabricated into the material is said to be embedded.
The epitaxy process is used to modify the material properties to within a few thousandths of a millimeter at the surface of a substrate. As the material is a single crystal, rather than a device simply fastened to the top of a substrate, an electronic charge can travel much more quickly through the material.
Typically, epitaxy is used to deposit alloys or compounds comprising two or more elements. By carefully selecting the composition of the elements, the structure can be made to respond to, or emit light at, specific wavelengths, from short wavelengths (UV) through the visible spectrum, to long wavelength light or infrared.
NEA:What are the main features and benefits of the different technologies used by IQE?
Dr Nelson:The initial substrates are produced using vertical gradient freeze (VGF) and liquid encapsulated (LEC) technologies. Both techniques are similar in principle in that either a seed crystal of indium phosphide (InP) is pulled from a melt of indium and phosphorous, or a gallium arsenide (GaAs) seed is pulled from a melt of gallium and arsenic, under precisely controlled conditions. As the melt is slowly pulled and rotated, it freezes to form a crystalline boule. This boule is sliced into wafers which form the starting material on which epitaxial layers are grown.
Early techniques for producing InP and GaAs included liquid phase epitaxy (LPE) and vapor phase epitaxy (VPE). Vapor phase epitaxy is also referred to as chemical vapor deposition (CVD). Molecular beam epitaxy (MBE) tends to be used for electronic devices requiring very precise layer control.
LPE is an inefficient process suitable only for simple structures of less than six layers. VPE is a process through which various gasses containing the required elements are flowed over the heated substrates.
MOVPE (or MOCVD, OMVPE, OMCVD) is the same as the VPE process but with the addition of metal organics (or organo-metallics). Metal organics are liquids or powders containing gallium, aluminum and indium, which can effectively be converted into gasses within the VPE equipment. The metal-organics part of the process is essential for facilitating the growth of materials such as gallium arsenide (GaAs), indium phosphide (InP) and other combinations. MOVPE is highly efficient at "growing" thicker layers (up to 10mm). Traditionally, MOVPE has been used to produce optoelectronic products.
With the MBE process, a range of sources are heated in an ultra-high vacuum (UHV) chamber. Traditionally, the MBE process has been used to produce electronic devices that need very sharp interfaces between layers as the level of control is much higher. But the process has slightly slower growth rates than is common with the CVD processes.
NEA:Which applications benefit the most from your products?
Dr Nelson:IQE offers a diverse range of materials systems for both electronic and optoelectronic devices. Pure silicon has a theoretical speed limit of around 2GHz. Current wireless applications typically operate at around 1.8GHz, and as we look towards future generations (eg, 3G telephony), we can anticipate the first applications that are likely to both breach the limit and need the lower power consumption offered by compound semiconductors.
As PC systems get faster, they too will breach the 2GHz limit, and compounds -- whether silicon based (SiGe, strained silicon) or GaAs/InP based -- provide the solution.
High-speed electronics encroaches upon many aspects of technology, and compound semiconductors may be found in space applications, medical devices and automotive systems, as well as consumer and communications products.
As for infrared and visible optical devices, these cover a range of applications, from displays to communications devices.
NEA:What makes IQE stand out from other key industry players?
Dr Nelson:With traditional silicon technologies, there are three basic discreet production stages: wafer supply, wafer fabrication and device packaging. The emergence of new technologies involves the introduction of a significant additional stage between wafer supply and wafer fabrication. This additional stage is epitaxy.
UMC, TSMC and Chartered offer downstream fabrication services for silicon chips. IQE offers enhanced materials (epitaxial wafers) as a foundry service.
As an epitaxial wafer foundry, IQE produces the materials that can be processed using the technology offered by wafer fabrication foundries such as UMC, TSMC and Chartered Semiconductor. As such, IQE's product offerings form a complementary stage in the supply chain.
NEA:Does IQE have any plans to establish a plant or business operations in the Asia-Pacific region?
Dr Nelson:IQE is considering joint ventures in the Asia-Pacific region. A plant or joint venture in Singapore or Taiwan would be ideal because of the proximity to the well-established wafer fabrication foundries, which would be potential customers for our advanced epitaxial wafers. The combination of IQE's materials processing expertise with the region's device processing expertise could offer a one-stop-shop for next-generation technology.
by Adeline Ong, Singapore
(August 2002 Issue, Nikkei Electronics Asia)
