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Intevac makes the POINT
Intevac M a k e s the POINT Following our feature in issue 1, we report on other new technical and product developments from Intevac MBE Equipment Division, Santa Clara, CA, USA. Firstly, we report on the new products: Heated Window Assembly, the Effusion Source Enhancement, POINT system and new substrate holder design and then on successful p-type doping of GaN at Boston University. I
ntevac has released news of ~a quartet of new MBE accessories and first we report on the new UHV heated window assembly (see schematic) which allows line-of-sight viewing into any UHV apparatus. while inhibiting deposits, such as As, from forming on the inner surface of the optical port window. A thermocouple is integrated into the window heater design and provides feedback to a controller, allowing window temperature regulation to the desired set-point. A user-settable controller maintains desired windowtemperature accuracy from room temperature to 400C. It is easily fitted onto any vacuum chamber with a s t a n d a r d 2.75-in conflat flange. A small, tabletop controller can be conveniently placed nearby and is connected to the assembly with cables. The product is currently in stock.
Effusion source enhancement The performance and capacity of Intevac's Low Defect Effusion Cell has just got better with the development of a Thermal Profile Insert. While the existing cell design has achieved the lowest defect densities reported, some users working with more than 75 grams of Ga have observed the presence of larger defects prior to completion of a number of calibration and evaluation runs. With the TPI several groups have demonstrated reproducible achievement of low defect densities from the first through to the last growth with fills of up to 125 grams. Thus the TPI results in not only lower defects, but significantly longer Ga fill life.
Substrate Holder Design Intevac's new high temperature, high uniformity, n o n - b o n d e d substrate holder for 2-in wafers has an im-
[
hltevac's U H V Heated Window Assembly is a specially-designed viewport window surrounded by a heater unit.
p r o v e d spring design. The new spring's feature increased spring lif~, reliable and precise wafer support and improved temperature uniformity. Film thickness uniformity across the wafers grown has been reported to be +/-0.2%. Current users can easily have their existing substrate holders modified for the new spring design.
P.type GaN Researchers at Boston University under the direction of Prof. T D Moustakas, recently announced that they were able to grow intentionally doped p-type gallium nitride (GaN) films (1). It is anticipated that this will lead to the development of high quality blue-UV light emitters based on the formation of p-n junctions. G a N is a direct, wide bandgap semiconductor ( E g - 3 . 5 e V ) which shows great promise for blue-UV optical devices. The potential of this material and other III-V nitrides has not been fully realised, largely due to
difficulties in intentionally doping this material n- and p-type. Recently, GaN films grown by MOCVD methods were successfully doped p-type by the incorporation of Mg (2,3). However, the films require a post-growth electron bombardment or high temperature annealing in order to activate the dopants, a result which has been attributed to hydrogen in the films. The Boston University team used an ECR microwave plasmaassisted MBE (ECR-MBE) to activate molecular nitrogen. The films which were produced in an Intevac Mod Gen II MBE system, have up to 1019 cm -3 holes without requiring any post-growth treatment.
The POINT Intevac's new POINT - POint of INflection Thermometry system and technique is a new a p p r o a c h to substrate temperature measurement. It offers significant accuracy improvement over p y r o m e t r y and other measurement techniques for in situ
MOCVO Equipment 5PI-MOCVD
I005
I n t e v a c ' s P O I N T r M - P O i n t o f I N f l e c t i o n T h e r m o m e t r v , s y s t e m a n d technique, a n e w a p p r o a c h to s u b s t r a t e t e m p e r a t u r e m e a s u r e m e n t . P O I N T offers w a f e r g r o w e r s an a e e u r a e y 10 times b e t t e r than p y r o m e t r y a n d 100 times b e t t e r than t h e r m o c o u p l e techniques.
determination of substrate temperatures during epitaxial growth, says Intevac. The epitaxial wafer grower now has the ability to accurately determine substrate temperature within +2°C. independent of film thickness, composition or emissivity and p r o v i d e s r e p r o d u c i b l e results to + I°C Research shows POINT's accuracy is a substantial improvement over other existing technology, up to 10 times better than pyrometry and 100 times better than thermocouple techniques. In addition, POINT provides material growers with the control and repeatability necessary for advanced material growth. "Previous substrate temperature measurement techniques have limited accuracy and repeatability caused by the effects of epilayer thickness and doping, underlying IRemitting surfaces and overcoating films in the optical p a t h , " said Richard J. Clark, general manager of the MBE Division at Intevac. " P O I N T overcomes these limitations and accommodates the wide range of substrate temperatures encountered in epitaxial growth." Using a transmission spectroscopy technique, P O I N T performs noncontact, in-situ measurement of the wafer temperature in the range of 20°C to 800°C during actual epi growth. Precise temperature measurement is insured by the incorporation of band gap compensation for the selected substrate material.
SPI-MOCVD
450
SPI-MOCVD
500XT
SPI-MOCVD
1200
Temperature Measurement POINT is configured as a 19" rack mounted controller with an optics platform and heated window assembly attached to the growth chamber. An optional feature provides closed loop control capability. Point is automated and operates unattended, and has a real-time graphical display as well as digital data storage and read out. The P O I N T system is currently being manufactured for solid and gas MBE systems growing on semiinsulating GaAs and InP substrates. This MBE market comprises over 800 systems worldwide. Developments underway will add other III-V and II-VI materials, doped and undoped, as well as adapting P O I N T to other UHV semiconductor equipment.
L? rl a " ' : ~
~ r
lis , [
Call Steve Hogan,
Equipment Division (61 7 ) 2 7 5 - 6 0 0 0
Contact. Richard Clark, Intevac, MBE Equipment Division, Tel/fax: [1] (408) 986 9888 / 727 7350.
References: 1. T D Moustakas and RJ Molnar, MRS
Proc. Symp. D, (Dec. 1992). 2. H Amano, et al. J. Electrochem. Soc., Vol. 137, 1639 (1990). 3. S Nakamura, et al. Japan, J. Appl. Phys., Vol. 30, L1708 (1991).
sp re For Information Circle 223
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ntevac has released news of ~a quartet of new MBE accessories and first we report on the new UHV heated window assembly (see schematic) which allows line-of-sight viewing into any UHV apparatus. while inhibiting deposits, such as As, from forming on the inner surface of the optical port window. A thermocouple is integrated into the window heater design and provides feedback to a controller, allowing window temperature regulation to the desired set-point. A user-settable controller maintains desired windowtemperature accuracy from room temperature to 400C. It is easily fitted onto any vacuum chamber with a s t a n d a r d 2.75-in conflat flange. A small, tabletop controller can be conveniently placed nearby and is connected to the assembly with cables. The product is currently in stock.
Effusion source enhancement The performance and capacity of Intevac's Low Defect Effusion Cell has just got better with the development of a Thermal Profile Insert. While the existing cell design has achieved the lowest defect densities reported, some users working with more than 75 grams of Ga have observed the presence of larger defects prior to completion of a number of calibration and evaluation runs. With the TPI several groups have demonstrated reproducible achievement of low defect densities from the first through to the last growth with fills of up to 125 grams. Thus the TPI results in not only lower defects, but significantly longer Ga fill life.
Substrate Holder Design Intevac's new high temperature, high uniformity, n o n - b o n d e d substrate holder for 2-in wafers has an im-
[
hltevac's U H V Heated Window Assembly is a specially-designed viewport window surrounded by a heater unit.
p r o v e d spring design. The new spring's feature increased spring lif~, reliable and precise wafer support and improved temperature uniformity. Film thickness uniformity across the wafers grown has been reported to be +/-0.2%. Current users can easily have their existing substrate holders modified for the new spring design.
P.type GaN Researchers at Boston University under the direction of Prof. T D Moustakas, recently announced that they were able to grow intentionally doped p-type gallium nitride (GaN) films (1). It is anticipated that this will lead to the development of high quality blue-UV light emitters based on the formation of p-n junctions. G a N is a direct, wide bandgap semiconductor ( E g - 3 . 5 e V ) which shows great promise for blue-UV optical devices. The potential of this material and other III-V nitrides has not been fully realised, largely due to
difficulties in intentionally doping this material n- and p-type. Recently, GaN films grown by MOCVD methods were successfully doped p-type by the incorporation of Mg (2,3). However, the films require a post-growth electron bombardment or high temperature annealing in order to activate the dopants, a result which has been attributed to hydrogen in the films. The Boston University team used an ECR microwave plasmaassisted MBE (ECR-MBE) to activate molecular nitrogen. The films which were produced in an Intevac Mod Gen II MBE system, have up to 1019 cm -3 holes without requiring any post-growth treatment.
The POINT Intevac's new POINT - POint of INflection Thermometry system and technique is a new a p p r o a c h to substrate temperature measurement. It offers significant accuracy improvement over p y r o m e t r y and other measurement techniques for in situ
MOCVO Equipment 5PI-MOCVD
I005
I n t e v a c ' s P O I N T r M - P O i n t o f I N f l e c t i o n T h e r m o m e t r v , s y s t e m a n d technique, a n e w a p p r o a c h to s u b s t r a t e t e m p e r a t u r e m e a s u r e m e n t . P O I N T offers w a f e r g r o w e r s an a e e u r a e y 10 times b e t t e r than p y r o m e t r y a n d 100 times b e t t e r than t h e r m o c o u p l e techniques.
determination of substrate temperatures during epitaxial growth, says Intevac. The epitaxial wafer grower now has the ability to accurately determine substrate temperature within +2°C. independent of film thickness, composition or emissivity and p r o v i d e s r e p r o d u c i b l e results to + I°C Research shows POINT's accuracy is a substantial improvement over other existing technology, up to 10 times better than pyrometry and 100 times better than thermocouple techniques. In addition, POINT provides material growers with the control and repeatability necessary for advanced material growth. "Previous substrate temperature measurement techniques have limited accuracy and repeatability caused by the effects of epilayer thickness and doping, underlying IRemitting surfaces and overcoating films in the optical p a t h , " said Richard J. Clark, general manager of the MBE Division at Intevac. " P O I N T overcomes these limitations and accommodates the wide range of substrate temperatures encountered in epitaxial growth." Using a transmission spectroscopy technique, P O I N T performs noncontact, in-situ measurement of the wafer temperature in the range of 20°C to 800°C during actual epi growth. Precise temperature measurement is insured by the incorporation of band gap compensation for the selected substrate material.
SPI-MOCVD
450
SPI-MOCVD
500XT
SPI-MOCVD
1200
Temperature Measurement POINT is configured as a 19" rack mounted controller with an optics platform and heated window assembly attached to the growth chamber. An optional feature provides closed loop control capability. Point is automated and operates unattended, and has a real-time graphical display as well as digital data storage and read out. The P O I N T system is currently being manufactured for solid and gas MBE systems growing on semiinsulating GaAs and InP substrates. This MBE market comprises over 800 systems worldwide. Developments underway will add other III-V and II-VI materials, doped and undoped, as well as adapting P O I N T to other UHV semiconductor equipment.
L? rl a " ' : ~
~ r
lis , [
Call Steve Hogan,
Equipment Division (61 7 ) 2 7 5 - 6 0 0 0
Contact. Richard Clark, Intevac, MBE Equipment Division, Tel/fax: [1] (408) 986 9888 / 727 7350.
References: 1. T D Moustakas and RJ Molnar, MRS
Proc. Symp. D, (Dec. 1992). 2. H Amano, et al. J. Electrochem. Soc., Vol. 137, 1639 (1990). 3. S Nakamura, et al. Japan, J. Appl. Phys., Vol. 30, L1708 (1991).
sp re For Information Circle 223
[z~iiii ~i::i!~il]~!ii~::ii~ii~::i~i~ii: .[i[~i::~i~ !i!i~i~i i~ii::i~i~::~i ~i~ ~ :~ . ~ ~' ~:* . • ~i:~: .+~
• ~.. "........... .
~. ....
>
~: ~ ••'~ "~i~i *~+"!'~:~ ~*•'"iiii!~!i!ii!!::~iiiii!i~ili i i i i~!iii::[ ::i::ii~::~:ii::::::{i:?:i~ii::i ~ii~/:i:/: ! ~ : i:ii:i:i:i