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MBE & OMVPE materials technology — Part II
M
tiler particularly stressed the advantage of the in-situ direct monitoring of epilayer available in MBE growth whereas this capability has yet to be developed for MOVPE. Given the subtle control and monitoring needed for advanced device structures, this could prove crucial for some applications. Considerable work is underway by a variety of companies to develop a corresponding system for MOVPE. T F R will be returning to these developments in a future issue but for now we turn to a comparison of the economics of MBE vs MOVPE.
Economics Compared 1 have chosen to compare two commercial reactors that have recently come on
MBE & O M V P E Materials Technology - P a r t II by Jeff Miller One of the h i g h l i g h t s of the IEEE GaAs IC Symposium is the Short Course. Last year it was a highly successful start to a successful conference and drew record attendance. The course was titled Digital IC Technology covering device technology and served as an introduction to the newcomer or as a refresher for the veteran. One of the papers TFR found particularly interesting was that given by Jeff Miller. In the second of two parts we are pleased to feature this article based on his presentation. The techniques themselves were described but for the purposes of this article we shall omit the larger detail and resume where the comparison began.
the market, in MBE the Riber Model 48 and in MOVPE, the Aixtron 2000. The machine cost for the Riber is about $1.6M while
the Aixtron is about $1M. Their capacities are similar - 7x2", 4x3" and 3x4" for the MBE and 5x3" for the MOVPE system.
l'hickness unilorlnity ix specified to be about 1"., on these, and the doping on the MBE is about 3% while on the MOVPF. it is about 1'!?,. The added capital facilities necessary to ulilise these systems probably run to $100k for liquid nitrogen systems I\)r the MBE and in the order of $0.5-1M lor the exhaust treatment high purity gases, toxic gas detection etc in the MOVPE system. This means thai total capital cosls are quite comparable. The figure shows some of the guesstimates 1 made on the cost per wafer under optimal conditions growing specific structures, not a range of structures, growing at I micron per hour on 3" wafers in two shifts with the structure about I micron thick. For the M BE system, this would resull in a staff requirement of about one expert and one technician per automatic loading machine so we can operate on two shifts without having anyone on hand. The MOVPE would require one expert and two technicians and perhaps some more facility support to keep those other facilities up and running.
Riber's model
Varian M B E system.
For Riber's model, 1 used a very detailed model of the output of these reactors. Typically it was felt you could achieve 8000 3" wafers per year on this kind of structure. I applied that model as best I could to the MOVPE system and came up with about 10 000 wafers per year. So if you look at these facilities and machine depreciation which amounts to about $40 per MBE wafer and about $32 tbr the MOVPE, material expenses for 1 micron growth are $4 and $20 respectively. The MOVPE materials arc
considerably more expensive and staff costs are slightly higher. Maintenance and machine calibration costs are also nonnegligible parts of the cost. The bottom line is that the MBE wafers are slightly less expensive than those from the MOVPE. I don't think this is necessarily of any great importance, it just illustrates the fact that these two techniques would probably cost about the same. And it would depend a lot on just how you operate the system rather than the actual physical cost.
Tough questions There are several tough questions that have to be answered in order to really see if these systems can be used for producing IC style wafers. The toughest question for M B E is whether this defect density of equal or better than lOcm -2 can really be maintained over long periods of time in a production environment. It's a question that really has to be answered. Secondly, is it possible to boost the growth rates in particular above 3 microns an hour and still maintain the low defect density? This is very important for MBE's ability to scale-up to meet wafer demands. This is an area where MOVPE has typically done very well. The next question must be, can the promised scaleup in MOVPE be realised? I think the answer is that with some of these planetary motion systems MOVPE will really give us uniformity across a run of wafers. The next question is, will run to run reproducibility really be sufficient? This question really needs to be answered in MOVPE and I
Produce nearly arbitrary doping or composition profiles Fast (for most FET doping) Fix backgating MESFETs JFETs HEMTs HBTs Requires high temp annealing
Ion Implantation
Epi
NO
YES
YES NO YES NO NO NO
NO YES YES YES YES YES
YES
NO
Q: Is Implantation dead? A: No! Epi will always need isolation Future of Epitaxial Material
Staff Machine and special facilities depreciation Material expended/lmm Staff Cost Maintenance Cost Machine Calibration 3" Wafers/yr Cost per wafer
1 expert 1 expert 1 technician/machine 2 technician/machine 40
40
4 20
20 24
2
2
7 8000
$7 10 000
$73
$93
Cost guesstimates per wafer (Based on lwn epilayer and 3in wafers) 2 shift lp.m/hr
Machine Cost Capacity/run Uniformity +composition thickness doping Added capital facilities
Capital Cost
MBE
OMVPE
1.65M 7x2" 4x3" 3x4"
1.0$M 7x2" 5x3"
1% 1% 1% liquid nitrogen
1% 1% 1% exhaust, exhaust treatment high purtty gases, toxic gas detection 600$K-I$M 1.65M-25M
1.75M
Costs and Capabilities
think tied to that is the question of whether any insitu monitoring will be developed for MOVPE. This is absolutely necessary to match the run to run reproducibility that's already been achieved by MBE. Lastly, I'd like to remind you that ion implantation isn't everything and in particular I believe that these epitaxial technologies will eventually replace implantation for ICs because the highest performance devices use heterojunction structures and that sidegating reduction is possible by epitaxy.
Two horse race The bottom line question is, will MBE or MOVPE grab the largest share of the market? I don't know. I think it's still a two horse race where they both have their attributes and they're sort of neck and neck at the moment. Dr. Jeff Miller Hewlett Packard Laboratories 3500 Deer Creek Road Palo Alto, CA.94304, USA. Tel: (415) 757 3251 Fax: (415) 857 2379
In Part I of this article, the caption on the photograph of the MBE system was incorrect. It should have read: Varian MBE system. We apologtse for this error and would like to point out that Varian MBE is now part of INTEVAC,
Readers are reminded that the Short Course from which this article was taken will be held again this year at the 1991 GaAs IC Symposium. This will be held on Sunday October 20th and is titled "Case Studies of Successful Product AppUcatioos of GaAs ICs". For further details please see Diary page.
tiler particularly stressed the advantage of the in-situ direct monitoring of epilayer available in MBE growth whereas this capability has yet to be developed for MOVPE. Given the subtle control and monitoring needed for advanced device structures, this could prove crucial for some applications. Considerable work is underway by a variety of companies to develop a corresponding system for MOVPE. T F R will be returning to these developments in a future issue but for now we turn to a comparison of the economics of MBE vs MOVPE.
Economics Compared 1 have chosen to compare two commercial reactors that have recently come on
MBE & O M V P E Materials Technology - P a r t II by Jeff Miller One of the h i g h l i g h t s of the IEEE GaAs IC Symposium is the Short Course. Last year it was a highly successful start to a successful conference and drew record attendance. The course was titled Digital IC Technology covering device technology and served as an introduction to the newcomer or as a refresher for the veteran. One of the papers TFR found particularly interesting was that given by Jeff Miller. In the second of two parts we are pleased to feature this article based on his presentation. The techniques themselves were described but for the purposes of this article we shall omit the larger detail and resume where the comparison began.
the market, in MBE the Riber Model 48 and in MOVPE, the Aixtron 2000. The machine cost for the Riber is about $1.6M while
the Aixtron is about $1M. Their capacities are similar - 7x2", 4x3" and 3x4" for the MBE and 5x3" for the MOVPE system.
l'hickness unilorlnity ix specified to be about 1"., on these, and the doping on the MBE is about 3% while on the MOVPF. it is about 1'!?,. The added capital facilities necessary to ulilise these systems probably run to $100k for liquid nitrogen systems I\)r the MBE and in the order of $0.5-1M lor the exhaust treatment high purity gases, toxic gas detection etc in the MOVPE system. This means thai total capital cosls are quite comparable. The figure shows some of the guesstimates 1 made on the cost per wafer under optimal conditions growing specific structures, not a range of structures, growing at I micron per hour on 3" wafers in two shifts with the structure about I micron thick. For the M BE system, this would resull in a staff requirement of about one expert and one technician per automatic loading machine so we can operate on two shifts without having anyone on hand. The MOVPE would require one expert and two technicians and perhaps some more facility support to keep those other facilities up and running.
Riber's model
Varian M B E system.
For Riber's model, 1 used a very detailed model of the output of these reactors. Typically it was felt you could achieve 8000 3" wafers per year on this kind of structure. I applied that model as best I could to the MOVPE system and came up with about 10 000 wafers per year. So if you look at these facilities and machine depreciation which amounts to about $40 per MBE wafer and about $32 tbr the MOVPE, material expenses for 1 micron growth are $4 and $20 respectively. The MOVPE materials arc
considerably more expensive and staff costs are slightly higher. Maintenance and machine calibration costs are also nonnegligible parts of the cost. The bottom line is that the MBE wafers are slightly less expensive than those from the MOVPE. I don't think this is necessarily of any great importance, it just illustrates the fact that these two techniques would probably cost about the same. And it would depend a lot on just how you operate the system rather than the actual physical cost.
Tough questions There are several tough questions that have to be answered in order to really see if these systems can be used for producing IC style wafers. The toughest question for M B E is whether this defect density of equal or better than lOcm -2 can really be maintained over long periods of time in a production environment. It's a question that really has to be answered. Secondly, is it possible to boost the growth rates in particular above 3 microns an hour and still maintain the low defect density? This is very important for MBE's ability to scale-up to meet wafer demands. This is an area where MOVPE has typically done very well. The next question must be, can the promised scaleup in MOVPE be realised? I think the answer is that with some of these planetary motion systems MOVPE will really give us uniformity across a run of wafers. The next question is, will run to run reproducibility really be sufficient? This question really needs to be answered in MOVPE and I
Produce nearly arbitrary doping or composition profiles Fast (for most FET doping) Fix backgating MESFETs JFETs HEMTs HBTs Requires high temp annealing
Ion Implantation
Epi
NO
YES
YES NO YES NO NO NO
NO YES YES YES YES YES
YES
NO
Q: Is Implantation dead? A: No! Epi will always need isolation Future of Epitaxial Material
Staff Machine and special facilities depreciation Material expended/lmm Staff Cost Maintenance Cost Machine Calibration 3" Wafers/yr Cost per wafer
1 expert 1 expert 1 technician/machine 2 technician/machine 40
40
4 20
20 24
2
2
7 8000
$7 10 000
$73
$93
Cost guesstimates per wafer (Based on lwn epilayer and 3in wafers) 2 shift lp.m/hr
Machine Cost Capacity/run Uniformity +composition thickness doping Added capital facilities
Capital Cost
MBE
OMVPE
1.65M 7x2" 4x3" 3x4"
1.0$M 7x2" 5x3"
1% 1% 1% liquid nitrogen
1% 1% 1% exhaust, exhaust treatment high purtty gases, toxic gas detection 600$K-I$M 1.65M-25M
1.75M
Costs and Capabilities
think tied to that is the question of whether any insitu monitoring will be developed for MOVPE. This is absolutely necessary to match the run to run reproducibility that's already been achieved by MBE. Lastly, I'd like to remind you that ion implantation isn't everything and in particular I believe that these epitaxial technologies will eventually replace implantation for ICs because the highest performance devices use heterojunction structures and that sidegating reduction is possible by epitaxy.
Two horse race The bottom line question is, will MBE or MOVPE grab the largest share of the market? I don't know. I think it's still a two horse race where they both have their attributes and they're sort of neck and neck at the moment. Dr. Jeff Miller Hewlett Packard Laboratories 3500 Deer Creek Road Palo Alto, CA.94304, USA. Tel: (415) 757 3251 Fax: (415) 857 2379
In Part I of this article, the caption on the photograph of the MBE system was incorrect. It should have read: Varian MBE system. We apologtse for this error and would like to point out that Varian MBE is now part of INTEVAC,
Readers are reminded that the Short Course from which this article was taken will be held again this year at the 1991 GaAs IC Symposium. This will be held on Sunday October 20th and is titled "Case Studies of Successful Product AppUcatioos of GaAs ICs". For further details please see Diary page.